DIY – Rear Axle / Differential oil change, with pics – for FAQ
 

DIY: Changing the oil in a base C6 rear axle / differential

If you are experiencing the common differential chatter noise on turns when cold (rubbing, scraping, clunking, grinding or chatter sound), changing the differential lubricant will rid the noise instantly, at least after doing a few figure 8's with the new lubricant in place.

For some, a simple differential lube change has proven to be the cure for many thousands of miles, and for others, it has only helped for just a few thousand miles. If you prefer to avoid the dealership and wish to take immediate action, change your differential fluid and you will get rid of the chatter noise for likely up to a few thousand miles minimum if not much more. It's a good first step in any case.

Overall, changing the oil in a base C6 rear axle / differential is very easy. If it’s your first time, this DIY article will at least give you an idea of what to expect.

This refers to base C6s only. Z06s have differential coolers (base C6's do not) and require a bit more effort. Z06s and export vehicles have different axle oil capacities than the base C6 as well.

First, run the car a while to get the axle oil warm. I ran my car about 40 miles. When I got back, the axle case was quite hot to the touch. 20 minutes after shutting off the engine, the mufflers were finally cool but the axle case was still hot. With this in mind, it is a good idea to wait about a half hour after shutting off the engine until the exhaust system cools down so you do not severely burn yourself… the axle and axle oil will still be very warm for good drainage.

You’ll need to get the car up off the ground a bit as in photos, but keep car LEVEL. First choice would be to use a real lift. Second choice, back the car up on Race Ramps and then jack the front end in order to level the car. Last choice (most laborious), jack the car from both front and rear.

http://www.davemiranda.com/images/0-jacked-11.jpg

Since you need to access the rear axle from the rear, you cannot block the rear with a jack. I had initially tried to use my 4-point jack system, but was not able to access the axle plugs with the rear jack and cross member adapter in the way. I had to add stands under the rear puck locations and then remove the rear jack and cross member adapter. I then added two extra screw jacks under the rear “preferred” jacking locations for extra support and safety. This worked out fine. But next time I think I’ll try backing up on ramps… would be easier.

The axle case has two plugs that must be removed… a fill plug and drain plug. The fill plug is on the rear vertical side of the case, the drain plug is on the bottom horizontal side of the case. Both plugs exist on the right half of the case (passenger side). Both plugs are identical in size / type.

http://www.davemiranda.com/images/0-diagram-11.jpg
http://www.davemiranda.com/images/0-drain-11.jpg

Put some cardboard down on the floor and have some rags on hand as you will inevitably spill / splash some oil. Place a drain pan directly under the drain and fill plugs.

Clean the areas around both plugs. Using a 3/8” drive swivel arm socket wrench and 10mm allen socket of about 1 – ¾” total length (as shown), loosen and remove the fill plug. (Always remove the fill plug before removing the drain plug) There are different ways of accessing this plug but the photos show one method that seems to work well and is easy. Note in the photos that the socket wrench handle extends down through the middle of the aluminum cross member. Some oil may start to drip out. If the plug is very tight, use a piece of pipe over your socket handle for leverage. Both my plugs did not require much effort to loosen… pipe was not needed.

http://www.davemiranda.com/images/0-wrench-11.jpg

http://www.davemiranda.com/images/0-wrench-12.jpg

Next, loosen and remove the drain plug. The oil will come blasting out and may splash in the pan so shield your face. Allow the axle to drain for a while. Mine was still dripping 12 hours later.

Clean the drain plug and area around the drain hole and install drain plug. Torque to 35 Nm or 26 lb/ft. I chose to torque by hand… basically just got it nice and snug. Do not overtighten. You could get a torque wrench on the drain plug easily if you wanted, but not on the fill plug. If you are not sure about the torque “feel”, use a torque wrench on the drain plug in order to get a good “feel” for what it should be, then do your best to apply that same “feel” to the fill plug using your regular socket wrench.

Time to refill the axle:

IMPORTANT: Read the latest GM TSB regarding rear axle chatter to determine which GM gear oil / additive and amounts you should be using. This info has changed over the years and is subject to further periodic change. The latest axle TSB (as well as previous axle TSBs) can be found in post #2 of this thread:
http://forums.corvetteforum.com/show...24&postcount=2

As of January 2008, the oil specified for use in the Corvette differential is Dextron LS Gear Oil 75W-90, part #88862624 (#88862625 in Canada). No additive is required or recommended – just add straight Dextron LS 75W-90 only.

Your C6 differential requires roughly 2 quarts (check manual and/or TSB for exact specs for your year / model). But be sure to have at least 3 quarts of oil handy since it is almost impossible to squeeze all the oil out of the bottles into the axle, plus you’ll likely spill some anyway.

Since you will not be able to get the oil bottles higher than the fill hole, you must pump or squeeze the oil up into the hole.

The GM oil bottles come with extra pointed nozzle caps and a short piece of clear tubing. I found this set up to be too short and too small a diameter, plus after a while the nozzle gets oily and the hose starts slipping off the nozzle no matter what you do. One solution is to buy an aftermarket fill tube at the local auto store. The product I found (at Pep Boys) is made by Hopkins Manufacturing, called a “FloTool”… it threads right onto the GM oil bottles and has a 12” long section of clear tubing attached… twice as long and larger diameter than what you get with the GM oil bottle. This FloTool fit really nice and made the oil fill a breeze.

http://www.davemiranda.com/images/0-flotool-11.jpg

Insert the tubing into the fill hole of the axle holding the gear oil bottle up between the mufflers and squeeze the bottle. You will see the oil flow through the tube and into the axle. One headache though is that you can only get about half or two thirds the contents of the bottle into the axle even if you squeeze / crush the bottle as hard as you can… so you need to refill the bottle and repeat. This is the main reason to have at least one extra bottle of gear oil on hand. I guess you’d need a pump of some type to really empty the entire bottle into the axle... but not necessary because whatever oil does not make it into the axle can be saved for the next fluid change.

http://www.davemiranda.com/images/0-fill-11.jpg

Note: I am holding the bottle upside down in the photo – was just posing in that shot – bottle nozzle should be as low as you can get it with relation to the rest of the bottle.

Add oil to the differential until oil starts dripping out of the axle oil fill hole. Then allow the oil to drip out for a bit to make sure the axle is not overfull. Again, it's important that the car is level. Reinstall fill plug.

http://www.davemiranda.com/images/0-drain-12.jpg

Once everything is buttoned up, it is recommended (per TSB) to run the car in a tight "figure 8" pattern about 8 or 10 times as soon as you possibly can after the oil swap. Many consider this an important step so do not overlook it.

Thanks to the forum and its members for much of the info in this DIY post! :thumbs:

Note: I was just alerted by member Paulct that the axle drain plug on 2005 models (at least on his 2005) sits above the leaf spring so that you cannot get an allen wrench straight in from below. The spring is in the way. An L-shaped allen wrench tool must be used so that it can be pivoted above the leaf spring. On my 2006 model, the spring is NOT in the way of the plug and you can easily get an allen socket straight into the plug from below. (see photos below) So if you have an `06 or newer C6, you will only need a good allen socket and socket wrench to do the entire job. If you have an `05 model, you will ALSO need an L-shaped allen tool and most likely a short piece of small diameter pipe for extra leverage on the L-shaped wrench. Thanks Paulct for the below "2005" photos.

We suspect this difference in drain plug position has to do with the differential case change between 2005 and 2006. For more info regarding differential differences between `05 and `06 models, click below link:
http://forums.corvetteforum.com/show...9&forum_id=101

http://www.davemiranda.com/images/0-drain-2005.jpg

http://www.davemiranda.com/images/0-drain-2006.jpg

Latest axle chatter TSB (thanks to member, calemasters):

Date: 01-09-2008
TSB: #07-04-20-002A
Document ID# 2048181

2005 - 2008 Chevrolet Corvette

Subject: Rear Axle Clunk and/or Chatter Type Noise on Turns
(Drain/Refill Rear Differential Fluid) #07-04-20-002A - (01/09/2008)

Models: 2004-2008 Cadillac XLR (Including V-Series and Export)

2005-2008 Chevrolet Corvette (Including Z06 and Export)

This bulletin is being revised to change the fluid recommendation and to remove the requirement of adding friction modifier. Please discard Corporate Bulletin Number 07-04-20-002 (Section 04 -- Driveline/Axle).

Condition:
Some customers may comment on a clunk and/or chatter type noise from the rear of the vehicle while making turns.

Cause:
This condition may be caused by slip/stick of the posi-traction clutch plates due to insufficient limited-slip axle additive. As plates slip and stick, a jumping or jerking feel occurs accompanied by a clunk noise.

Correction:
Important: DO NOT remove the differential cover from the rear or the two sides. It is not necessary to flush the old fluid from the differential.

Drain and refill the rear differential fluid using the procedure listed below.

Draining Procedure:
Raise and support the vehicle. Clean any dirt from around the differential drain plug. If not equipped with a differential cooler, remove the drain plug (1) and washer (2) from the differential.

If equipped with a differential cooler: 4.1. Using a bent tip screwdriver, remove the quick connect fitting retaining ring (3) from the quick connect fitting (4) and discard the retaining ring.

4.2. Remove the differential cooler inlet pipe from the differential nut.

Drain the fluid.

Filling Procedure:
If not equipped with a differential cooler, install the drain plug (1) and washer (2) to the differential. Tighten the differential drain plug to 35 N•m (26 lb ft).

If equipped with a differential cooler: 2.1. Install a new retaining ring.

2.2. Connect the differential cooler pump inlet pipe (2) to the differential. A distinct snap should be heard or felt when assembling the cooler pipe to the fitting.

2.3. To ensure the cooler line is properly installed, give the cooler pipe a gentle pull.

Clean any dirt from around the differential fill plug. Remove the fill plug and washer from the differential.

Important: DO NOT add any limited-slip additive (friction modifier). With this new fluid (Dexron LS Gear Oil 75W-90) it is no longer required to add friction modifier. If friction modifier is added, it will cause the fluid to lose some of it's friction reducing properties as well as reducing seal life.

Fill the differential with the new DEXRON® LS gear oil, P/N 88862624 (Canadian P/N 88862625). Refer to the table listed below for lubrication specifications.

Check the fluid level to ensure it is even with the bottom of the fill plug hole to no lower than 6 mm (0.25 in) below the opening. Install the fill plug and washer to the differential. Tighten the differential fill plug to 35 N•m (26 lb ft).

Important: Steps 8-13 are for vehicles equipped with the differential cooling system. For vehicles not equipped with the cooling system, proceed to step 14.

Raise the vehicle so the wheels are about a foot off the floor. Make sure the wheels can spin freely without obstruction from the hoist or any nearby items. Start the vehicle and put the transmission in second gear. Slowly accelerate to 10 mph and hold this speed for one minute. Turn the vehicle off. Raise the vehicle. Check the fluid level in the differential. Add fluid until the recommended level is reached. Lower the vehicle.

Once the differential fluid has been changed, the vehicle must be driven in 8-10 tight figure eight maneuvers to heat the fluid and allow the fluid to be worked into the clutch plates.

Lubrication Specifications Application

2004-2005 XLR (Including Export) and 2005 Corvette (Non Export)
1.72 liters
1.85 quarts

2006-2008 XLR (Including V-Series and Export) and 2006-2008 Corvette (Non Z06)(Non Export)
2.0 liters
2.11 quarts

2005 Corvette Export
1.88 liters
1.99 quarts

2006-2008 Corvette Export (Non Z06)
2.16 liters
2.28 quarts

2006-2008 Corvette Z06
2.75 liters
2.91 quarts

Parts Information:
Description: DEXRON® LS Gear Oil
Part Numbers:
88862624 (US-1 Quart)
88862625 (Canada-1 Liter)

Warranty Information
For vehicles repaired under warranty, use:

Labor Operation: F9709*
Description: Drain & Refill Rear Axle Fluid
Labor Time: 0.6 hr

* This is a unique labor operation number for bulletin use only. It will not be published in the Labor Time Guide.

© Copyright General Motors Corporation. All Rights Reserved.

Document ID# 2048181
2005 Chevrolet Corvette

-------------------------------------------------

Previous axle chatter TSB (thanks to member, 99ssconv):

Date: 4-16-2007
TSB: #07-04-20-002
Document ID# 1961528

Subject: Rear Axle Clunk and/or Chatter Type Noise on Turns (Drain/Refill Rear Differential Fluid and Add Specified Limited-Slip Axle Additive)

Models:
2004-2007 Cadillac XLR (Including V-Series and Export)
2005-2007 Chevrolet Corvette (Including Z06 and Export)

Condition:
Some customers may comment on a clunk and/or chatter type noise from the rear of the vehicle while making turns.

Cause:
This condition may be caused by slip/stick of the posi-traction clutch plates due to insufficient limited-slip axle additive. As plates slip and stick, a jumping or jerking feel occurs accompanied by a clunk noise.

Correction:
Important: DO NOT remove the differential cover from the rear or the two sides. It is not necessary to flush the old fluid from the differential.

Drain and refill the rear differential fluid using the procedure listed below. Add the increased amount of limited-slip axle additive specified below.

Raise and suitably support the vehicle.
Clean any dirt from around the differential drain plug.
Remove the drain plug and washer from the differential.
Drain the fluid.
Install the drain plug and washer to the differential.
Tighten the differential drain plug to 35 N·m (26 lb ft).

Clean any dirt from around the differential fill plug.
Remove the fill plug and washer from the differential.
Important: Prior to adding the limited-slip axle additive, the bottle MUST be shaken vigorously for at least 1 minute to mix the additive thoroughly, then immediately poured into the differential.

Add 237 ml (8.0 oz) limited-slip axle additive, P/N 1052358
(Canadian P/N 992694).

Fill the differential with synthetic axle lubricant, P/N 89021677
(Canadian P/N 89021678).

Check the fluid level to ensure it is even with the bottom of the fill plug hole to no lower than 6 mm (0.25 in) below the opening.
Install the fill plug and washer to the differential.
Tighten the differential fill plug to 35 N·m (26 lb ft).

Lower the vehicle.
Once the differential fluid has been changed, the vehicle must be driven in 8-10 tight figure eight maneuvers to heat the fluid and allow the additive to be worked into the clutch plates.

Part #: 89021677 (89021678 In Canada)
Description: Synthetic Axle Lubricant
Quantity: 2 (3 for Z06 and Export)

Part #: 1052358 (992694 In Canada)
Descrption: Limited-Slip Axle Additive
Quantity: 2

For vehicles repaired under warranty, use:
Labor Operation: F9709*
Description: Drain & Refill Rear Axle Fluid
Labor Time: 0.6 hr

*This is a unique labor operation number for bulletin use only. It will not be published in the Labor Time Guide.

© Copyright General Motors Corporation. All Rights Reserved.

Document ID# 1961528
2006 Chevrolet Corvette

----------------------------------------------------------

Previous TSB - 12/06/06 (thanks to member, vetteshop):

Subject: Rear Axle Chatter Shudder On Turns - keywords bind differential #PIP3559F - (12/06/2006)

Models: 2004 - 2007 Cadillac XLR
2006-2007 Cadillac XLR-V
1999 - 2007 Chevrolet Corvette, Corvette Z06

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Rear axle chatter or shudder on turns on Chevrolet Corvette and Cadillac XLR.

Recommendation/Instructions:
Flush and fill the rear axle with synthetic axle lubricant GM P/N 89021677 (Canadian P/N 89021678) and appropriate amount of the friction modifier additive P/N 01052358 (in Canada 992694). See fluid amounts listed below.

Note 1: In some cases it has shown that a second flush procedure on a second repair visit will correct the chatter/shudder concern prior to replacement of the clutch packs.

Note 2: To properly flush the rear differential remove the left differential cover and get all of the old fluid out off the differential, wipe out the residue replace the cover o-ring and then reinstall the cover and fill with the appropriate amount of fluid and friction modifier additive.

If the complaint or the condition persists after the flush and fill, replace the right and left rear axle clutch packs following published service procedures.

After clutch pack replacement use synthetic axle lubricant GM P/N 89021677 (Canadian P/N 89021678). and the appropriate amount of friction modifier additive P/N 01052358 (in Canada 992694). See fluid amounts listed below.

Note 3: PRIOR TO INSTALLING THE FRICTION MODIFIER ADDITIVE FOR EITHER OF THE ABOVE REPAIRS THE BOTTLE MUST BE SHAKEN VIGOROUSLY FOR AT LEAST 1 MINUTE TO MIX THE ADDITIVE THOROUGHLY.

Once the axle fluid has been changed the car must be driven in 8 - 10 SLOW figure eights to work the fluid between the clutch plates.

Fluid capacity:
Model Year
Model
Differential Lube
Friction Modifier

1999-2005
Corvette ALL
1.69 qt (1.6L)
4 oz. (118 ml)

2006-2007
Base Corvette
1.95 qt (1.85L)
5 oz. (148 ml)

2006-2007
Corvette Z06
2.70 qt (2.55L)
6.4 oz. (190 ml)

Note 4: Export vehicles use 2.01 l (2.12 qt) synthetic axle lubricant GM P/N 89021677 (Canadian P/N 89021678) and approximately 150 ml (5.1 oz) limited-slip differential lubricant additive GM P/N 1052358 (Canadian P/N 992694).

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

-----------------------------------------------

Previous TSB - 10/13/06

Subject: Rear Axle Chatter Shudder On Turns - keywords bind differential
#PIP3559C - (10/13/2006)

Document ID# 1866944
2006 Chevrolet Corvette

2004 - 2007 Cadillac XLR
2006 - 2007 Cadillac XLR-V
1999 - 2007 Chevrolet Corvette, Corvette Z06

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern: Rear axle chatter or shudder on turns on Chevrolet Corvette and Cadillac XLR.

Recommendation/Instructions:
If this is the first complaint for this condition flush and fill the rear axle with synthetic axle lubricant GM P/N 12378261 (P/N 12378261 has been replaced with P/N 89021677), (Canadian P/N 10953455) and appropriate amount of the friction modifier additive P/N 01052358 (in Canada 992694). See fluid amounts listed below.

Note 1: To properly flush the rear differential remove the cover and get all of the old fluid out off the differential, wipe out the residue and then reinstall the cover and replace the fluid and additive.

If this is a repeat complaint or the condition persists after the flush and fill, replace the right and left rear axle clutch packs following published service procedures.

After clutch pack replacement use synthetic axle lubricant GM P/N 12378261 (Canadian P/N 10953455). and the appropriate amount of friction modifier additive P/N 01052358 (in Canada 992694). See fluid amounts listed below.

Note 2: PRIOR TO INSTALLING THE FRICTION MODIFIER ADDITIVE FOR EITHER OF THE ABOVE REPAIRS THE BOTTLE MUST BE SHAKEN VIGOROUSLY FOR AT LEAST 1 MINUTE TO MIX THE ADDITIVE THOROUGHLY.

Once the axle fluid has been changed the car must be driven in 8 - 10 SLOW figure eights to work the fluid between the clutch plates.

Fluid capacity:

1999-2005
Corvette ALL
Differential Lube: 1.69 qt (1.6L)
Friction Modifier: 4 oz. (118 ml)

2006-2007
Base Corvette
Differential Lube: 1.95 qt (1.85L)
Friction Modifier: 5 oz. (148 ml)

2006-2007
Corvette Z06
Differential Lube: 2.70 qt (2.55L)
Friction Modifier: 6.4 oz. (190 ml)

Note 3: Export vehicles use 2.01 l (2.12 qt) synthetic axle lubricant GM P/N 12378261 (Canadian P/N 10953455) and approximately 150 ml (5.1 oz) limited-slip differential lubricant additive GM P/N 1052358 (Canadian P/N 992694).

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

------------------------------------------------------

Previous axle chatter TSB: 9/08/06

Subject: Rear Axle Chatter Shudder on Turns - keywords bind differential #PIP3559A - (09/08/2006)

Models: 1999-2007 Chevrolet Corvette
2004-2006 Cadillac XLR
2006-2007 Cadillac XLR-V

This PI is being superseded to update recommendations, models and years.
Please discard PIP3559.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Rear axle chatter or shudder on turns on Chevrolet Corvette and Cadillac XLR.

Recommendation/Instructions:
If this is the first complaint for this condition flush and fill the rear axle with mineral based lubricant P/N 89021669 (in Canada 89021670) gear lube and 4 ounces of the friction modifier additive P/N 01052358 (in Canada 992694).

If this is a repeat complaint or the condition persists after the flush and fill, replace the right and left rear axle clutch packs following published service procedures.

After clutch pack replacement use 1.6 l (1.69 qt) synthetic axle lubricant GM P/N 12378261 (Canadian P/N 10953455). and 4 ounces of the friction modifier additive P/N 01052358 (in Canada 992694).

Note: 2006 Z06 equipped vehicles require 2.55 l (2.70 qt) synthetic axle lubricant GM P/N 12378261 (Canadian P/N 10953455) and approximately 190 ml (6.4 oz) limited-slip differential lubricant additive GM P/N 1052358 (Canadian P/N 992694).

Note 2: Export vehicles use 2.01 l (2.12 qt) synthetic axle lubricant GM P/N 12378261 (Canadian P/N 10953455) and approximately 150 ml (5.1 oz) limited-slip differential lubricant additive GM P/N 1052358 (Canadian P/N 992694).

Once the axle fluid has been changed the car must be driven in 8 - 10 SLOW figure eights to work the fluid between the clutch plates.

Note 3: PRIOR TO INSTALLING THE FRICTION MODIFIER ADDITIVE FOR EITHER OF THE ABOVE REPAIRS THE BOTTLE MUST BE SHAKEN VIGOROUSLY FOR AT LEAST 1 MINUTE TO MIX THE ADDITIVE THOROUGHLY.
------

A few other bits of interesting info:

*Member vetteshop stated: “…in the past,I have replaced a bunch of clutch packs in the C5's, they have the same issue. Upon inspection of the removed clutch packs, they do not fail, they look brand new with no evidence of wear or damage. The issue seems to be a varnish buildup on the plates that causes binding, resulting in the noise when turning. This is why replacing the fluid (with new additive) may only temporarily cure the problem. The problem is the design of the rear differential. Caprice's and Camaro's with posi rears have had the same issue for years. The difference on the Corvette is that there is not a cover that you can remove to clean the clutch packs, such as every other conventional posi rear end. The only way to clean the clutch packs is to remove the rear from the vehicle and completely disassemble it. One may as well install new clutch packs after going through all that trouble…”

*Member calemasters stated: “…Original axle clutch plates were fiber. New plates are carbon… I believe BG production changed to the carbon plates in late December of 2005… I spoke to one of the Getrag engineers (he used to be on this board) but he was not clear to why the grind chatter occurred with the fiber plates. Just that the carbon plates fix this condition… Time it takes to replace clutch packs: With Automatic Transmission, 7.2 hours; With Manual Transmission 6.7 hours ”

*Member jabbott of Rat Pack Motorsports stated: "These are some of the symptoms (chatter, etc) of a Posi Traction unit. Usually you can change the oil or add some slip additive and it will go away. Changing the clutches is not going to make a difference. There are only two ways to solve it (eliminate chatter) and they both require a lot of work if the oil is not doing the trick. You can have some of the carrier machined where the clutches go in, we do this to fine tune our race clutch setup but it could also be done for a street car to help with chatter. The second is we can install a torque biasing carrier which you would never have chatter again. Both of these are very expensive options, in the end the chatter is not going to hurt anything mechanically, it is more just an issue with the driver thinking something is wrong."

*Member shopdog stated: "To do any good, the additive has to be worked in to the clutch packs. Since the diff is a splash system, it is sometimes hard for the slickum to find its way into the clutch packs before it settles out (isn't miscible in the diff oil). That's why the TSB says to drive the car in figure 8s immediately after adding it. That makes the clutches slip, and lets some of the slickum slip into the clutches too. I have a suspicion that not all of the cars at the factory get driven that way right after the diff fluid is added. Anyway, a few ounces more additive in the differential won't hurt anything. I wouldn't suggest putting 5 pints of additive in, but an extra 4 ounces is cool."

*Member shopdog stated: "You need to realize that the differential is a splash lubrication system. If the car sits for several days without being driven, the lube drains out of the clutches. Then when you first drive it again, the clutches are working dry until enough lube works its way back up there to relube the clutches. This causes uneven wear of the clutches, and after doing this enough times, you get chatter..."

*Member mbonness posted these interesting polls regarding axle chatter:
http://forums.corvetteforum.com/show...ight=axle+poll
http://forums.corvetteforum.com/show....php?t=1516122
http://forums.corvetteforum.com/show....php?t=1525645

*Here's a post by a member with continuing noise issues even after clutch pack and fluid changes:
http://forums.corvetteforum.com/show....php?t=1558897


---

Thank you very much
 

You did a great job on the article. The fluid in the rear end needs to be changed because all new mechanical parts wear in and it is a good idea to get all those little metal particals out. Thanks again for all the info.

:hurray: Great job!

Went underneath my 2005 C-6 and the rear end says "Getrag" on it.

Nice write-up :thumbs:

Great write-up.
I have 2 questions:
Are the drain and fill plugs the same?
If so, are they the same as a C-5?
Reason is, I'm thinking of replacing the fill plug with a C-5 magnetic drain plug. Should catch the steel "dust" and allow removal without draining the diff.

Both the drain and fill plugs use Torx bit sockets to loosen or tighten!!
 

In your article you mentioned Allen heads on the drain and fill plugs, they are actually Torx heads, probably a T-30 or T-40 size, and will require a set of Torx bit sockets in 3/8" rachet size. Hope this helps.
Most everything now uses Torx screws, bolts, plugs, etc.

Unless I missed it, you did not mention to remove the FILL plug first.

Always remove fill caps/plugs first. If you ever drain something and cant get the fill cap off, you are pretty screwed.

:iagree: :lurk:

I'll address a few questions here:

Thanks! Both the drain and fill plugs are exactly the same on the C6. I have no idea whether or not they are the same as those on the C5, hopefully someone else can chime in and help you on that. I meant to measure the plug diameter and pitch when I had them out but I forgot... sorry! :)

The plugs on my car are definitely allen, not torx. Take a look at the photos. It is very possible that some axles come with allen plugs and some with torx plugs... whatever they have on hand. I'm sure both exist and are common.

http://www.davemiranda.com/images/0-drain-12.jpg

Indeed and agreed. Yes, if you follow the article from beginning to end you'll note that I say to remove the fill plug first. I guess I just forgot to explain why. Thanks! :thumbs:

Wow! What a good job on the DIY. I love this forum.

To clear up any possible confusion... all C6s have the Getrag axle. What calemasters is saying is that it was reported to him that Getrag switched from fiber clutch plates to carbon clutch plates in December 2005 in attempts to solve the cold chatter problem.

My car was built in November `05 and I have the cold chatter problem... I guess I have the "old" fiber plates. I wonder if anyone with a car newer than December `05 has the chatter problem...?

That sounds like a good topic for a poll. I think I will go ahead and post one right now...

Not on my car. Both plugs have M10 Allen heads. Vet's photos also show what are clearly Allen-head drain plugs.

10mm Allen plugs here also.

So what if we have the chatter and do nothing. Will it hurt anything either short or long term?

Very good question. Because if nothing is getting damaged, there's really no need to worry about it at all. Having a little scrubbing noise for the first few minutes of operation is not a problem.

If the issue really is varnish on the plates, then it would make sense that the plates themselves may not get damaged for a long time if at all.

I wonder if by ignoring the issue for a while the noise would eventually happen full time as opposed to just a few minutes after a cold start. That would be a problem.

Quick update...

I changed the oil in my axle using the non-synthetic oil and additive as outlined in the TSB. Upon backing the car out of the garage right after the change, the noise was still there, but that makes sense since at that point the oil hadn't been worked into the clutches yet. I then drove the car for about 20 miles, including doing about eight figure-8s in a parking lot. Put car away.

Took the car out again a few days later... cold scrubbing noise completely gone.

I find it quite interesting that a mere oil change can have such an immediate effect on this problem.

I was planning on changing the oil one more time soon in the name of performing a true "flush".... with hopes of having the axle behave at least throughout the winter... so I don't need to crawl under the car in 20 degree weather :).

Any theories on why a mere oil change instantly kills the noise? I had thought that maybe the fresh oil cleaned varnish off the plates... but you'd think it would take a while for that to happen if that was the case, not just 20 miles and a few figure 8s.

All the more reason to do a true flush, meaning changing the oil out two or maybe even three times. Because apparently, whatever was in that axle (the old synthetic oil itself, or varnish...???) was causing or greatly contributing to the noise, thus getting as much of it out as possible would be the best thing.

I took the car out yet again yesterday... no noise.

Thoughts?

Wow - what a terrific write-up with excellent illustrations and suggestions! Every do it yourself project should be so well documented! (And not just about Corvettes, either!)

Thank you very much!

My theory is that the noise is caused by the clutch plates actually rubbing together without any fluid between them, causing the grinding noise you hear basically due to lack of lubrication. After you drive around for a few minutes the fluid gets worked in between the plates, but only temporarily, and after you park it the fluid doesn't stick to the clutch plates and sort of drains away.

Now with the limited slip "additive" I think somehow the fluid sticks in between the clutch plates better so it's still worked in there when you go out to start the car in the morning and you won't hear the noise, i.e. your clutch plates are better lubricated now and they will tend to stay that way longer.

Excellent post :thumbs: Many thanks

Interesting. That makes sense. That would certainly explain why the clutch packs only make noise after the car hasn't been run in over 5 hours or so, and then stops making noise after a few turns.

Remember though, the "additive" is supposed to be added to both the GM sythetic oil (at the factory and otherwise), and also to the non-synthetic oil. So, it's not just a matter of adding additive. The additive should already be in there from the factory... unless they screwed that up at the factory.

Assuming the factory put in the correct stuff, then we are saying that the synthetic oil itself might be a problem... since the TSB says to put in the NON-synthetic. However, the TSB does say to use synthetic IF the clutch packs are being changed... unless they are assuming that the replacement clutch packs are made of a new different material that can better deal with the synthetic oil... carbon as opposed to fiber as has been reported.

But... I don't think the oil can really "drain away" from between the clutch plates so quickly, additive or no additive. To my knowledge, the clutches are pressed together tight under spring load... I'd think that any decent oil would stay on those surfaces... at least for a pretty long time... as a film.

This is why the varnish theory sounded good... because if there was some sticky "varnish" on the plates, the plates would tend to stick together after being pressed against each other for over 5 hours and cooling off. The varnish would be softer and slipperier when hot, and then get harder and stickier when cold. When you'd first run the car cold, the sticky surfaces would tend to grab / rub together... then once enough fresh oil would be introduced over that sticky surface, the plates would then start to run smoothly. Again, just a theory.

Would be really neat if we had a Getrag engineer here to just tell us the EXACT cause of the noise and explain, etc. Unless they are baffled too! :lol:

Thanks! :thumbs: :cheers:

Thanks to all here who have left kind words. Much appreciated!

I am happy to contribute to the forum whenever possible. I've learned so much here, the least I can do is try to put something back now and then.

And thanks to the many others at the forum who have posted great DIY articles and other excellent informative info!

:cheers: :cheers: :cheers: :cheers:

Sounds plausible. To add to your varnish theory I also found out that when contaminants get into the rear axle fluid over time (i.e. metal particles from manufacturing imperfections) it can cause rear axle chatter, so when you perform the drain/flush and refill you are effectively removing the metal-saturated oil and providing "clean" fluid.

Just wondering, are you going to regularly change your axle oil now based on an arbitrary maintenance schedule (i.e. every 5000 miles) or just wait until you start hearing the noise again?

My 2006 Z51 continues to make sounds while turning no matter how many miles I drive (so far about 50 at one time). Took it to dealer today, they said they could do nothing other than visual inspection for damage. Dealer said GM was aware of the problem, trying to come up with a fix, but - DO NOT ATTEMPT TO REPAIR - no fluid change, nothing. Does anyone know the official treatment as of today? Help!

Good question. I plan on changing the oil once again real soon... like maybe after another 100 miles or less... so that I will have truly "flushed" the axle out good. At that point I think it will be safe to say that I have 100% clean fresh oil in the axle with essentially no trace of whatever was in there previously.

It does actually make a lot of sense to continue to change the axle oil at regular intervals to PREVENT the noise from coming back. However, I might just run this new oil until the noise DOES come back, just to see how long it'll take. Technically, you should not have to change the axle oil at all... so... would be interesting to learn if this new oil would actually cure the problem for good... or... even if it kept the axle quiet for say 30k miles, I'd consider that a fix. But if the axle makes noise again less than 3k miles later or so, then... :ack: :rofl: :banghead: Changing the axle oil every 3k miles for the life of the car would be a headache.

Well, I had gone almost 11k miles before the noise started... so in theory, unless the clutch plates are "damaged" in some way at this point, I'd expect I could potentially go another 11k miles before any noise creeps back... who knows.

I will report back periodically.

You have the right idea,but based on my experience I believe that the additive simply does not mix well with the synthetic fluid and tends to seperate and drain to the bottom.We used to have some sucess by removing the synthetic and replacing it with standard gear oil and additive when flushing with synthetic didnt work.GM even recomended this in a TSB.This is why flushing the rear and performing tight figure eights tends to get the additive up into the clutch packs and temporarily eliminates the noise.

Hi vetteshop... interesting. :thumbs:

What about the varnish you had mentioned you had found in many of the chattering axles you rebuilt? Any idea how the varnish got there... and why? How might the varnish and oil type be related... if at all? Based on your experience with these axles, what would be your recommendation for those experienceing the cold chatter problem? At the moment, I am betting on just swapping in the non-synthetic GM gear lube along with the GM additive (as per TSB), and just hoping for the best.

Bookmarked

Guys, you're gonna think I'm really nuts this time :crazy:, but... I just noticed the new addition to the axle chatter TSB: "PRIOR TO INSTALLING THE FRICTION MODIFIER ADDITIVE FOR EITHER OF THE ABOVE REPAIRS THE BOTTLE MUST BE SHAKEN VIGOROUSLY FOR AT LEAST 1 MINUTE TO MIX THE ADDITIVE THOROUGHLY"....

Ok... this reminded me of something... when I had purchased four bottles of GM rear axle friction modifier additive recently at a local Chevy dealer, I noticed that one of the four had a DIFFERENT odor than the rest. :confused: :ack:

No, I do not regularly test the odor of automotive fluids :)... but I just happened to remove the top on one bottle and took a sniff... it had a strange odor... I was then compelled to sniff the others. The other three had the same exact odor as each other (an odor I recognized from past axle fluid changes)... the one other bottle though had a noticeably different odor... pretty strange actually.

I was not going to bring the odd smelling additive back to the dealer because they'd surely think I was insane. At the same time, it was very obvious to me that something was up with this one bottle of additive and I had no way of figuring it out... and I was NOT going to take any chances with my axle... so I discarded this bottle of additive... oh well, $7 or whatever down the drain, no biggie.

But now, based on this above new addition to the TSB, I am wondering if maybe the one strange smelling bottle of additive I had just needed to be shaken well...? I did not try shaking. Maybe after a vigorous shaking the odor would have changed...?

Also note... the GM non-synthetic gear oil comes in SEALED bottles... good. The GM additive DOES NOT come in sealed bottles. The top screws right off and there is NO seal at all. In theory, a dealership stock boy could accidentally spill some additive out of the bottle and then replace it with whatever. Another reason I just discarded my odd smelling additive... really had no idea what was in that bottle. It did LOOK correct visually... but... not taking chances.

I was not going to post this bit of odd and admittedly "nutty" info, but when I saw that new addition to the TSB, it got me thinking.

Plus... I wonder why it is apparently so important to shake the additive before adding it to the axle. Because once inside the axle, it's all going to get mixed really well anyway. I guess they are just concerned that a certain part of the additive might remain in the bottle and never make it into the axle.

???

Uhhhh...And, uh, what, uh...exactly did...it...smell, uh...like? :leaving: :rofl: :rofl:

Yep, Vet, my man yer bonkers...you need to take a vacation from all things Corvette. OTOH, you may very well have stumbled onto the very reason why GM is having to pay out tens of thousands of dollars for noisy differential warranty work...some little pinhead stock boy has been peeing (or something) in their anti-slip additive. :lol: :lol:

Shhhhh...Let's just keep this between us...You might as well be trying to tell the General you were abducted by space aliens. :rofl:

:lol: :lol: :lol:

I know, sounds crazy, but... it is apparent that the friction modifier additive itself is a critical part of eliminating chatter. That tiny 4 oz bottle of stuff can make the difference between an axle that is dead quiet and one that is a chatter box.

The shop manual stresses that it is critical to put the exact correct ratio of additive to gear oil in the axle... as well, the latest TSB states in all caps that the 4 oz bottle of additive must be shaken vigorously for 1 minute before adding to axle, etc.

Point is, that 4 oz of additive is indeed a critical key. If for some reason one were to get a "bad" bottle of additive (either a bad batch from the factory, or one that someone tampered with), that will almost definitely cause trouble.

The one "odd" bottle of additive I received smelled noticeably different than the other three. Again, these bottles are not sealed from the factory. Not sure how one can accurately identify additive, but odor is indeed an observable property. I think I'd be more concerned about an incorrect odor than an incorrect color... to a degree anyway.

As crazy as it all sounds, I think the insane asylum jury will let this one slide :)... with all this axle trouble everyone is having, the last thing anyone should do is put something in the axle that they are not CERTAIN is a good batch of the correct GM friction modifier additive.

Man, I was just reading the shop manual regarding a tear down and rebuild of the rear axle... necessary to change the clutch packs... boy, that is one serious job. Getting the axle out isn't so terrible, but the tear down and rebuild is heavy-duty. A LOT more involved than the axles of yesteryear. If the technician doing the work isn't a highly experienced ace, I think your axle will be doomed and you'll be going back more than once to have it rebuilt again and again.

I personally would recommend doing anything possible to avoid having your axle rebuilt if at all possible... unless you know the technician personally and know he's rebuilt at least 10 Getrag axles successfully. So... right now I am hoping like hell the oil change is going to keep my axle happy for a good long time! :thumbs:

can't remove drain plug
 

I got the fill plug loosened just fine, but because the rear spring blocks the drain plug, there is not enough room to get the 10mm allen and a 3/8" sockect wrench in there! Or an extension.

Whats the trick, and can you post which tool you used, and where to get one? Thanks!

Paul

:thumbs: Great DIY post.

i got one of the first c6's so this should be a issue for me but i have never noticed....bullets and lg's may be the reason ..... but has anyone tried just doing figure 8's before changing to see if this stops the problem. i do not see where puttting in new oil is going to chang things in a new car. yes need to flush to remove any particulates from new rear end but other then that?

I have not heard of anyone who tried the 8-10 figure 8s as a remedial fix for the problem, but I did notice myself the sound would kind of come and go from one day to the next so I questioned whether I was doing something just by turning differently etc. It seems quite possible you could spread the fluid around better by doing some figure 8s as a temporary fix, but once you have the angle "fit" between the clutch plates you're doomed and you could do all the figure 8s you want and it wouldn't really solve anything. The additive seems to play a major factor since my car rides 100% smoother now since they did the fluid change about a month ago...

not sure if it matters or not, but I changed my fluid out to Royal Purple with the built in friction modifier at around 1000 miles just for the heck of it. I wasnt aware of any chatter issue at that point, but the stuff I took out stunk REALLY bad and was pretty nasty looking. I haven't had any chatter at all yet, not sure if I'm lucky or its because of the Royal Purple, or it just hasnt started yet. Car has approx 7k on it now.

Hi Paul - to get the drain plug out, I used the same exact wrench and allen socket that I used to get the fill plug out. The drain plug on my `06 Z51 coupe is NOT blocked by the rear spring. I have a clear photo of my wrench on the drain plug if you need it... let me know.
:cheers:

:thumbs: Now in the FAQ... great job!

Doc
:cool:

Update added to first post of this thread... near bottom.

Member Paulct alerted me to the fact that the rear spring in his `05 model partially blocked access to the axle drain plug... unlike on my `06 model. For details, see update in post #1.

http://forums.corvetteforum.com/show....php?t=1497063

:thumbs:

changed mine..... 6000 miles....
used to make noise after sitting for a few hours.....

NOT ANY MORE.... :thumbs:

thanks for the info.... :cheers:

2006.... 10mm (not torx).... no problems....
will probably change it one more time in about 200-500 miles (just to see what color the oil is)

Excellent DIY, Thanks. :thumbs: :thumbs: :flag:

Ref: Chatter in relation to build date...
 

My '06 was built 1/12/06 and chatters like a nudist sunbathing at the north pole. Now has 13.5K miles. Has been chattering since about 8K. Dealer is willing to do fluid change. I plan to get that done soon and will report back with results. Just for kicks, I also plan to do the figure 8's this afternoon after work and see if it helps any and, if so, how long it lasts. Don't expect any improvement, but why not try it and see for sure!

My '06 now has ~14K on it and I've done some auto X's with it so I am thinking of changing out the diff fluid (already did the MN6 tranny) but I am confused as to using the mineral base or synthetic fluid? So far no rear end noise so this is strictly a preventative maintenance issue. Please help me decide what fluid is best suited for my needs! :willy:

Great Job! Thanx for posting this :thumbs:

Being that so many C6s start chattering at around 8k - 12k miles, chances are high that you will eventually experience it too. The solution so far, short of changing the clutch packs, is to swap in the MINERAL oil. That's what GM tells us to do in the TSB. So if it were me, I'd put in the mineral oil.

Don't get fooled into thinking that synthetic is "better" than mineral. GM posi rears used mineral oil since day one and have lasted very long with no problems. I know some would rather eat nails than use oil other than synthetic because they feel synthetic is far superior, but try to put that illusion behind you.

The TSB also says to use synthetic IF putting in new clutch packs, but keep in mind that, as far as we know, the "new" clutch packs are made of a different material than those installed in C6s before 12/05... and at this point may even be different than later ones too. So, it is possible that the engineers spec synthetic for the "new" replacement clutches only (due to their composition which may be more synthetic-friendly), and know that the factory clutches need mineral instead. Just theorizing... but when in doubt, follow the TSB.

Or you could just leave your differential alone until it starts scrubbing.

:cheers:

Just updated the differential fluid change DIY... added the latest 10-13-06 TSB... thanks to retrorod for providing that. Figured I'd bump this thread anyway since there seems to be a lot of axle related activity today.

Anyone want to hear from an old fart?

GM limited slip differentials have long become noisy after some miles. I'm not sure about the solid rear axles, but independent suspension rear gear cases have long done this.

An 'additive' has been specified as long as I can remember. I'm sure the orginial fill in all Corvettes has the additive in it, it's not just for noisy clutches. Regular gear oil smells bad, and the additive just makes it worse.

(You wanta hear the story about whale oil? The 'original' additive was supposed to be made from whale oil/blubber. When whaling products were banned in the US, GM had to develop a synthetic version of this. I'm not sure about the truth of this, may just be an early 'urban legend'.)

A usual fix for the noise was driving in about 5 tight right hand circles, then about 5 tight left hand circles, or about 5 figure 8's. This was supposed to work the clutches and open the surfaces up, getting oil/additive into the clutch packs. The noise basically came from the clutches not slipping for come time and getting dried out of oil. The tight turns worked the oil back into clutches and eliminated the noise.

I don't remember what milage it started at, but my 1972 did start noise and the figure 8's quieted it right down.

Has anyone with a noisy C6 actually tried the circles/8s before a dealer oil replacement? I would like to know if the old solution will still work on the new car?

I'm researching doing this changeout myself at the next oil change, as I've had the chatter recent mornings leaving the driveway, and often driving just slow speeds.

Now, I just want to make sure I'm reading this right... regarding the new TSB (10/13/06) in post#2: are the lubricant & additive part #s the same for both "first complaint" and "repeat complaint"?

Thanks!

Yes. Per the latest TSB (10-13-06), only the GM synthetic axle lubricant (#12378261) and GM friction modifier additive (#01052358) are designated to go into the differential, regardless of amount of complaints.

What does not make any sense to me is why replacing the differential fluid with the same stuff that was already in there is supposed to cure the problem. It would seem, at best, to be merely a temporary cure.

At least when the non-synthetic mineral oil was being specified for use by the previous TSB, we thought that maybe the engineers had discovered that the synthetic oil ITSELF was causing a problem with the clutch packs... and it made sense to drain the synthetic and put in the mineral.

But now that they are specifying the synthetic, it either means that the oil itself had nothing to do with the problem (and thus a mere oil change is nothing more than a temporary fix), OR, they have no idea what they're doing and are just guessing, wasting everyone's time. Only time will tell at this point.

based on all the experiences (and various intermediate solutions) with the roof issue, i'm going with the above.

Think I'll hold off on replacing the clutch packs myself, though if it comes to that :D

(edit-addon question): where can I get my hands on some of the gm-spec lubricant/additive? Do any of the forum vendors sell this stuff, or should I just walk into a dealer and confuse the heck out of some salesperson?

I had the noise on my 05 at about 4k miles. Went to the dealer to complain about it and they told me it would cost around $300 to change the fluid because it's suppose to be routine maintnance. I just left because I didn't feel like arguing with the idiot. I then went and bought 2 qts of Royal Purple 75/90 and swapped the fluid myself. I have 10k miles now and 6 months later, the noise went away and never came back after I swapped the rear fluid.
It was worth the $25 I spent on the fluid and the hour of my time to not have to drop my car off at the dealer.

Any GM dealer should have it... just be sure to give them the exact part numbers. I'd think the GM parts forum vendors (such as Fred Beans and Ken Fichtner) would have it too... perhaps give `em a try:

Ken Fichtner
email: kenfichtner@fichtnerchevrolet.com

Gene@FredBeans
email: gculley@fredbeans.com

I have called several Chev dealers plus one large Cadillac dealer in the Los Angeles area. None of them has had any one come in with this rear end growl complaint so I suspect no Chev service department (or Cadillac dealer) in the Los Angeles area has performed this fluid change or clutch relpacement.

I have the noise problem on my 2006 C6 but I am going to wait.

When, exactly did GM production switch to the new clutch plates?

Isn't the latest TSB stating to use the synthetic oil rather than the mineral oil?

Only thing that makes sense is that the new oil you put in has worked in and around everything in the axle by your doing the extra figure 8s.

What a pain. I think I will change the oil myself AFTER I get the car back tomorrow from my roof "fix."

Thanks for the very helpful information.:)

Thanks! :cheers:

Yes, synthetic is now specified for the flush per the latest TSB (10-13-06). Refer to the first three posts of this thread for the most updated info.

I will continue to keep the first few posts of this thread as updated as possible at all times. The part you quoted above must be from later in the thread, but prior to the new TSB... thus not updated.

Thanks again! :thumbs:

Get this...called my local Chevy service manager and explained this "chatter" problem. These guys say they have never heard of it. I explain the bulletin to them and they say they will have to test it.
Darn, if I knew I was going to have this much hassle with getting warranty work done I don't think I would have bought this car. I'll change the fluid myself.

Unless the labor runs over 2 hours they want me to sit in a waiting room and wait on the lovely thingee with the rest of the girls (ladies, don't take this the wrong way). Spending this kind of money, I am not used to wating in a customer service area...hmmm, wish Lexus sold Corvettes...they sure treat you a lot better. Heck, I could have bought a used Caddilac and gotten a rental car from the get go....no 2 hour labor issue involved.

Guess this is what happens when you go back down to buy a Corvette...sorry, had to vent.

Hey, even bought the GMPP MAJOR Guard and they don't want to treat customers any better...saying they have to go by Chevy rules...last time I looked I thought GM owned Chevy. Don't want to give me a rental car.

Sorry....had to spit this out. I think I will be doing my own work on the car from now on...wish I could fix the roof without taking it in.:ack:

I am debating whether I have this problem on the '05 I just purchased. Sometimes when turning slowly the rear makes a sound, almost like the rear tires are rubbing the fenderwell. Is this what it sounds like? In any case I am going to replace the fluid for peace of mind. When I replaced the output shafts in my C5 I had originally bought the GM synthetic fluid and additive. I bought some seals and other things at the same time and didn't think about the total. When I got home I realized that Mr Goodwrench charged me a fortune for the synthetic diff fluid. I can't remember the amount but I do remember being outraged enough to go return it and get a couple bottles of Royal Purple which already has the additive in it. This leade me to my first question:

Looks like only one person on this thread has tried aftermarket diff fluid. He was happy, anyone else? We have been using Royal Purple in the C5 diffs for years without any issues and this is what I plan to use in my C6 diff.

Secondly, I don't see any magnetic diff drain plugs on any sites like Ecklers or Mid America. They have them for the C5's and I am wondering if they would work for the C6 ('05 and '06+) diffs. Anyone know? Seems like another measure of protection to capture any small metalic filings floating around in there couldn't hurt.

:cheers:

Thanks. I will cetainly try that before I change it MYSELF. I will not fool with the dealer for this issue unless the changing of fluid does not work.

Hate going to the dreaded dealer...too bad some dealers are so bad about customer service...gives you a bad taste.

:iagree: :iagree: :iagree:
I'm with you, brother. No way I will let a Chevy dealer work on my car unless I just can't do the work.

Like the roof.

:)

I agree... I don't trust anyone. I do all my own work if and when possible.

However, having said the above, some dealers are indeed better than others. Many Chevy dealers out there barely even know what a Corvette is, let alone know any details about them, or how to fix them.

Then there are other Chevy dealers that deal with lots of Vettes, and in some cases are even Corvette-specific.

There will of coures be a BIG difference in the quality of the service and work you will get between going to a shop that sees one Vette a month, and a shop that works on several Vettes a day.

I purposely purchased my C6 from a local Corvette-specific dealer for this reason... and paid probably a bit more than necessary verses if I had spent lots of time and effort shopping all around looking for a cut-throat deal. Every time I go into their shop (to buy parts, fluids for my C6 and other GM cars, etc), there are ALWAYS Corvettes in the lot, on the lifts, etc... they even do Vette mods and performance tunings there. I don't know how good they truly are, but at LEAST they have their hands on Vettes everyday... and that's worth a lot in my opinion. At least I know they aren't going to crack the rocker panels or make other foolish errors that GM mechanics with little or no Vette experience often make.

Try to find a dealer within a reasonable distance of your location that sells and/or works on lots of Vettes if possible. That would be the place to go if you can. Might even be worth a long drive to know that your car will be repaired by someone with Vette experience.

Another big plus of going to a place that deals with lots of Vettes... all the people there are surrounded by Vettes all the time, they will have no interest in taking your car out for a violent joy ride, verses a backwoods shop that never even saw a Vette before where every lot boy and mechanic will be foaming at the mouth to get a chance to do burn-outs with your car as soon as you leave.

I guess it's always a headache... oh well. Hopefully we can just minimize the amount of dealer visits. I'm going on a year now with no need for the dealer, hope this trend continues.

:iagree: :iagree:
Those are good points you have made. Two Chevy dealers in my town and they do not sell a lot of Vettes. One does have a seemingly good mechanic that just works on Vettes. Nevertheless, I will be doing the work I can do...just don't want the hassle.

If I could fix the roof I would do that too. However, there will always be some things I will have to take the car to the dealer for.

You can bet if there is a next time, I will buy from the largest Corvette dealer I can find within two hours of me...and, I do know of one...wish I had bought mine from him.

Thanks for your excellent informative posts.:)

From one old fart to another, have you heard about putting in two bottles of the additive? I remember friends doing that years ago but I haven't heard it lately.:thumbs:

Come to think of it, this is an interesting idea. Might possibly be a quick easy end-all "cure" for those who drive VERY conservatively.

To my knowledge, putting in more additive than specified will not allow adequate gripping of the clutches, thus little or no posi operation... the rear will act like a non-posi. Please correct me if I'm wrong.

BUT... to many here at the forum, this may not matter. If one does not race or mash the loud pedal down on a regalur basis, one may not really miss not having a true "posi". For those who drive very conservatively, I guess the only time a posi is really helpful is when the road is wet... but conservative C6 drivers probably don't take their cars out in the rain anyway. Traction control would help here in any case, protecting from excessive wheel spin / over-revving.

Techies, chime in... can adding extra additive to the differential cause any other problems other than the reduction or loss of the posi function? Because it IS possible that putting extra additive WOULD keep things quiet... forever. And this may be a very attractive course of action for some.

Me... I need to have the posi working, so I would not try this personally. I was actually tempted to put a little extra additive in last time, not a whole extra bottle, but maybe an extra ounce or two, but I did not do it... kept things by the book.

[QUOTE=Vet]Come to think of it, this is an interesting idea. Might possibly be a quick easy end-all "cure" for those who drive VERY conservatively.

To my knowledge, putting in more additive than specified will not allow adequate gripping of the clutches, thus little or no posi operation... the rear will act like a non-posi. Please correct me if I'm wrong.

BUT... to many here at the forum, this may not matter. If one does not race or mash the loud pedal down on a regalur basis, one may not really miss not having a true "posi". For those who drive very conservatively, I guess the only time a posi is really helpful is when the road is wet... but conservative C6 drivers probably don't take their cars out in the rain anyway. Traction control would help here in any case, protecting from excessive wheel spin / over-revving.


:smash:
Surprise surprise. Took the Vette in today and they "foamed" the roof and, much to my surprise, put in new synthetic gear lub AND two of the additives. I have to eat a little crow for thinking it was going to be a bad experience. They actually took care of both issues with my one trip. I really could not believe it. All in all, it took 2 1/2-3 hours. But, I was very happy with the results so far. In fact, although they "foamed" the top, they said I had no separation. The service manager asked me if I was satisfied and I told him so far I was. He said to please state that on the Chevy/GM survey on this work, and that I was completely satisfied. Seems these surveys mean a LOT to somebody. I must admit I was a little cold after receiving a rather cold response to my issues with the Vette. But, hey, people surprise you sometimes.

Now, I hope the roof stays on and the NOISE stays away.:)

One thing, last night I did 8 figure eights in the parking lot. This morning the noise was still there, but not nearly as bad.

I'll update after this fluid change...thought I was going to have to do it myself. I will do 8 more figure eights tonight with the new lub and additive being put in today. :)

C4 Info! Calling For C4 Info! ('92 Thru '96)?
 

Alright everyone, where is the same INFO for all of us broke C4 owners?:( That was a very detailed explanation for C5's & 6's.:yesnod:
—ANYBODY???:toetap: THANKS.:bigears

Just a guess but maybe on the C4 forum.:cheers:

Vet,

Outstanding report and how to info! :thumbs:

Thank You :flag:

Thanks! :cheers:

I did try the figure eights and didn't help...off for roof recall / rear end combo fix this morning.:crazy:

Permanent fix
 

2 quarts of this:

https://www.amsoil.com/storefront/svg.aspx


1 bottle of this:

https://www.amsoil.com/storefront/ada.aspx


No more noise, ever- not just a few thousand miles.

Hell, I didn't even use the Sliplock additive- I had this problem on my Jeep that had a true-trac LSD. Mobil one turned black within 3 thousand miles, and often let out a BANG at highway speeds. Severe gear went on for 50k, no noise, no chatter.

2005 C6 With Differential Chatter and More
 

I have been reading the C6 differential chatter posts. I have the same problem and had it from day one--December 15, 2004. Several attempts by the dealer leave me in the same boat within a few miles...maybe 2 to 3K. However, I also get tightness in shifting and find that smooth shifts with the six speed and with out the obnoxious "clunk" on clutch release become difficult as the chatter and groaning continue to get worse. I live in a warm climate, it's not just a cold weather thing here.

I wondered if anyone else has encountered the rough shifting issue along with the diferential chatter? Thanks and let me know what you think.

Clunking Nois on C5
 

We have an '04 Le Mans Z06 that has acquired the same sort of noise described on this thread. I notice the TSB Bulletin specifically refers to C6's only. Does anyone have a copy of this bulletin they can share with me? Has this clunking noise ever been associated with C5's?

Z06 diff fluid change
 

Any Z06 owners done their own diff fluid change yet?? My car was built Jan 24, 2006 and my diff chatters like crazy. The dealer did the mandatory fluid change as the first step last spring at approx 10k miles. It helped for a while but now the chatter noise is back worse than ever at over 18k. Hot or cold makes no difference during parking lot turns. I really don't want the dealer to change out the clutch packs.

I plan to buy 3 qts of the Amsoil Severe Gear Synthetic EP 75W90 and 2 bottles (8 ozs total) of the Amsoil Slip Lock Additive to do my own change. The Z diff apparently drains via disconnecting the pump inlet tube at the diff bottom connection fitting. Some sort of spring clip holds this quick connect fitting together. Is this really an easy disconnect?? Shop manual says that the spring clip should be discarded and a new one used upon reassembly. Any advice or helpful hints??

Thanks

Many of us including myself have had good luck using the Amsoil product! Changed mine and the chatter was gone in 3 mins... I've read the problem is most pronounced with cars that don't get driven a lot. Don't know if that's true but mine wasn't a DD.... It started chattering bad around 6000 miles but it's not driver all winter. So far so good with Amsoil. It's the first time I've used any of their products but "IF" it keeps working I'll try more of them........ BTW the Z takes more fluid so you might want to ask the experts over there......
good luck

ttt

:lurk:

Sticking Clutch Packs Will Ruin Rear Tires!
 

GM's three (3) required complaints of rear end chatter, snapping, banging, etc., because of sticking clutch packs will cause flat spots on rear tires because differential will NOT slip in turns. I had to go 16k miles and 17 months before GM would replace clutch packs under warranty. As a result, I ended up with flat spots on my rear tires with still 10k miles on them. I had to buy new tires to reduce tire noise in the rear. DON"T let anyone tell you that BAD clutch packs will not hurt anything, because that is incorrect. I had to spend $800 for new tires that were damaged by defective clutch packs, you should have heard the tire noise.:cheers:

Wow, that's really unusual. If indeed the flat spots on your tires were caused by the differential, you must have had a very severe case of sticking clutches.

When my differential was chattering at its worst, my tires were definitely not skidding or skipping... I had loud chattering and shuddering in the rear (which indicated the clutches were indeed slipping, even though reluctantly) but no skidding tires. No damage to tires and no damage to my very soft and sensitive asphalt driveway (which readily reveals skid marks if and when a skid occurs).

Sounds like your clutch plates fully locked up somehow. Perhaps that's what happens if differential chatter is neglected long enough without a fluid change... GM should have changed the fluid in yours right away, that would have or at least should have cured it, at least for a while.

I have several thousand miles on my car since my last differential oil change... and I had used the old non-synthetic GM oil with just 4 ounces of additive (that's all that was called for at the time)... on a cold morning if the car has sat untouched for over a week I'll get a slight faint chatter when I first pull out (I need to make a very sharp turn as soon as I exit my garage), so the chatter is just starting to come back now... I plan to put the new Dextron LS stuff in soon and hope that holds for at least 10k - 20k miles. If so I can live with that.

Wow, flat spots on the tires... that's insane... were you hearing tire screeching and smelling burning rubber every time you went around a sharp turn? I'd think you'd need to really drag the skidding tire a decent amount to create a flat spot. If you had just minor occasional random skidding I don't think it would create flat spots but would just wear the tire quicker overall, little by little. But flat spots...:eek: :eek: :eek:!

At times the differential would sound like a hammer hitting it when on concrete and created small flat spots on the tire. I tried to get them (GM), even BG when I was there and they said it was not an safety issue; therefore, a dealer issue and GM bulletins said you had to bring it in three (3) times with the noise problem. The fluid and additive fix would not solve the proiblem only deferred and created more tire wear. They used the GM bulletin directive of delay, delay, and delay, that is why the tires got badly worn and still gave trouble. GM warranty service many times is not your friend. I found on many other repairs I would have to take the car in three times because of no parts, misadjustment, and shoddy work, it always was delay, delay, and delay and hassel, hassel, and hassel. I was even asked if I bought the car from the dealer, like a Corvette Tax, when it was $2,700 cheaper at another dealer. At the BG factory I was told there that I had a Vette in the top 2% of trouble (worse case). Unbelievable!:ack:

Sorry to hear of your troubles. That is indeed an unusual case. In most cases just changing the fluid eliminates the sticking and chatter. In fact the lastest differential TSB does not even mention changing the clutch packs at all (as it once did)... fluid change only. What you had was apparently a lot worse than what most of us have. Where it seems most C6s have the occasional cold chatter easily fixed with a fluid swap, you had a truly "defective" differential issue. There HAVE been a few cases of differentials that were not cured with only a fluid swap, but this seems to be the minority. GM probably kept blowing you off because they just assumed you had the "typical" chatter problem like most of the other C6s, fixed by a fluid change... but in fact you had something worse. As long as the car is good now.

:cheers:

Found out today at my chevy dealer Dexron LS Gear Oil 75W90 p/n 88862624 = $ 25.00/bottle.
Mobil 1 LS 75W90 at the Kragen store = $ 10.00 / bottle !

Contact Gene Culley on this forum.... I just purchased three bottles of the correct Dextron LS from him for about $15 a bottle... shipping wasn't bad either, like $6 or $7 if I remember correctly... so even with shipping, you're looking at about $17 per bottle. Considering all the trouble C6 owners have had with chattering differentials, I'd vote to use the exact "correct" fluid recommended by Chevy (Dextron LS)... the Mobil 1 might be fine, but there's a possiblity it could "give out" sooner than the Dextron would. So far I have not heard one single report of a chattering differential using Dextron LS... lookin' good!

Gene Culley - GM Parts House
gculley@gmpartshouse.com

:thumbs:

:iagree:


http://i236.photobucket.com/albums/f...ot/DEXRON2.gif


Place your order here:

http://www.trademotion.com/partlocat...&siteid=214638 :thumbs:

11 months and 9k miles later, my DIY change to AMSOIL Severe Gear with their Slip Lock additive is keeping my diff quiet. :D DEXRON LS was not available when I did the DIY.

I read recently that MOBIL is the supplier (manufacturer) of DEXRON LS to GM. If so, the quality & specs of the two products should be identical.

Nice writeup.

Long story short- I had bad chatter. My axles sounded like they had a locker in them.

Dealer put additive in, no worky.

I got Dexron LS and changed it out, oil fluid was black and stinky, new fluid was nice and clean. Did 20 mins of figure 8's. Problem went away.

3K miles later I repeated the change procedure to make sure all the old stuff got out of there- a "flush" of the diff, I guess.

No issues since. Diff has been exposed to long high speed runs that produce hi temps, and no issues. Dexron LS works. The severity of the noise prior to changing the fluid had me thinking my rearend was in need of full replacement. This did not turn out to be correct.

KISS- change to LS, do figure 8's, and enjoy the quietness.

Great DIY writeup. Thank you.

Great DIY writ up! :thumbs:

I actually took mine to the dealer to get done since I did not have the means for the DIY. They drained and refilled with the new GM oil and all seems well for now. Just hope it stays that way.

Thanks guys :cheers:

Indeed... KISS!!!... :thumbs::thumbs::thumbs:

:iagree:I would stick with the GM Dextron because of warranty issues UNLESS you are over that and/or willing to pay to play.

Man, I can't believe it was that simple. My 2007 A6 w/Z51 has been chattering for a few thousand miles (odo currently 12,142) but only when I pulled out of my garage and made the 90 degree turn to the street and again when making the 90 degree turn at the STOP sign on my street. Once warm it never happened. After reading all the "chatter" posts in here I decided I had the problem. Yesterday I went to my Chevy dealer and bought 3 quarts of the new magical pixey dust fluid from GM that's supposed to fix this problem. Drained, refilled, first trip out of the garage and no noise. Drove to parking lot and did 6 figure 8 patterns, came home for the night. Today I ran to Lowe's and not once did the chatter return. Hopefully this fix is permanent. I'm impressed that fluid change can have a dramatic effect instantly.

Rear end noise when turning
 

Rear end noise Clanking Grinding FYI
I was in Scottsdale last weekend when I noticed a grinding noise coming from the rear end. I was little worried about this as I live in San Diego and it is about a 5 hour trip. I went to the Corvette Forum and got all kinds of advice but I ended up with a little different twist which I wanted to share. Unlike most of the owners that experience this and simply change the rear end oil with the friction additive and the problem goes away. As we know this problem usually is the positraction disks not working properly and the new oil generally does the job.
I took my 2005 C6 in for a 50,000 mile service and they recommend that you change the transmission oil and the rear end oil as part of the service which they did. After a week I started to hear the rear end noise, just the opposite of what most people experience noted above. I took it back to the dealer this week and they knew what ithe problem was and they ended up changing all the disks a major job. Thank goodness the extended warranty paid for it. They did have to get approval from the GM zone manager. It was at the dealer a week. They did a great job but this is a different twist which may help someone out when experiencing this problem.

Rear end noise when turning
 

Rear end noise Clanking Grinding FYI
I was in Scottsdale last weekend when I noticed a grinding noise coming from the rear end. I was little worried about this as I live in San Diego and it is about a 5 hour trip. I went to the Corvette Forum and got all kinds of advice but I ended up with a little different twist which I wanted to share. Unlike most of the owners that experience this and simply change the rear end oil with the friction additive and the problem goes away. As we know this problem usually is the positraction disks not working properly and the new oil generally does the job.
I took my 2005 C6 in for a 50,000 mile service and they recommend that you change the transmission oil and the rear end oil as part of the service which they did. After a week I started to hear the rear end noise, just the opposite of what most people experience noted above. I took it back to the dealer this week and they knew what ithe problem was and they ended up changing all the disks a major job. Thank goodness the extended warranty paid for it. They did have to get approval from the GM zone manager. It was at the dealer a week. They did a great job but this is a different twist which may help someone out when experiencing this problem.

I highly doubt there could be a warranty issue...the tech spechs are the same.

I'm just trying to point out that some of the dealers can be a real pain in the bun and make some common sensibles, VERY UNSENSIBLE (some dealers are unbelievable).:cheers:

:flag:I put Amsoil Severe gear 75-90 with 4oz of Amsoil friction modifier in mine 10,000 miles ago and still not a single sound; quiet as a mouse.:):)

Nice write-up, Thanks :thumbs: :thumbs: