Bad00SS

I have an 07 Z and have been noticing a rattling/grinding noise only on slow speed right hand turns. It is coming from the rear. possibly drivetrain related. I hear it puling into parking spaces and into driveways or if i do a u turn in a circle thats in my neighborhood. do you think i broke something in the CV part of the axle from launching it? Its hard to pin point what this is but its definetly got me worried.

dmuellenberg

Sounds like your rear differential fluid needs to be changed. Here is the TSB on it.

Document ID# 2048181
2005 - 2008 Chevrolet Corvette


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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)




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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).


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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
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
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
Quantity

Metric
English

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
Part Number
Description

88862624 (US-1 Quart)

88862625 (Canada-1 Liter)
DEXRON® LS Gear Oil


Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

F9709*
Drain & Refill Rear Axle Fluid
0.6 hr

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 It will not be published in the Labor Time Guide.




GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
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© Copyright General Motors Corporation. All Rights Reserved.

2k Cobra

I owned an 07 Z with the same problem.

After changing to the new (at the time) fluid and doing figure 8s on a parking lot, all was well.

Great info mentioned above..

2k

Bad00SS

Looks like I am going to have the corvette tech at my local dealer drive it tomorrow on lunch break and see if he agrees this is the problem. if so I will have him change the fluid after work for cash.

Sox-Fan

Is it primarily in one direction? I think you said right only?

Does it sound like a brake rotor rubbing? could you have a hub getting worn out?

Bad00SS

it does it in forward and reverse. only right hand turns.

Bad00SS

Got it to the dealer. It is now making the noise both right and left turns. its pretty bad now. The tech says he still believes its the clutches in the posi unit grabbing and chattering. hes gonna do a fluid change and see how it is. He says from his experience it will never 100% go away but it will get alot better. Found that odd that there is no guaranteed fix without buying a new differential assembly. I will know more tomorrow most likely.

Landru

Weird as it sounds, good thing it's doing it so a tech can address it.
G/L, keep us posted on outcome.

dmuellenberg

Changing the diff fluid should fix the problem, but if it doesn't then the only fix will be to replace the clutch packs. I had to replace mine but it was under warranty.

Too-Fast

It may be a long shot, but pretty simple to check the rear lug nuts...

Axle Nut TSB:

Bulletin No.: 07-04-95-001A

Date: May 29, 2008

Subject:
Tapping or Scraping Noise From Rear Wheel Area (Replace Wheel Drive Shaft Nut)

Models:
2005-2009 Cadillac XLR
2005-2009 Chevrolet Corvette

Supercede:

This bulletin is being revised to add the 2009 model year. Please discard Corporate Bulletin Number 07-04-95-001 (Section 04 - Driveline/Axle).

Condition

Some customers may comment on a tapping or a scraping noise coming from the rear wheel area.

Cause

This condition may be due to the torque on the wheel drive shaft nut relaxing over time.

Correction

Replace the left and the right wheel drive shaft nut following the procedure below.

1. Remove the center cap from the rim.

2. Remove and discard the wheel drive shaft nut.

3. Apply LOCTITE(TM) 272 or equivalent to the threads of the axle shaft.

4. Install the nut (P/N 10257766) and tighten to the new specification.

Tighten

Tighten the nut to 215 N.m (160 lb ft).

5. Install the center cap to the rim.

Important: The vehicle should not be driven for 24 hours following the repair in order to allow the thread lock to cure.

Parts:

1/2" 34mm socket $10.39 ships free ( )

2 GM#1025-7766 axle nuts $2.89 each +shipping ( http://www.oehq.com/oeparts_GMP10257...-NUT-FWD/S.htm )

LocTite RED 271 $9.95 +shipping ( http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32 )





Tools:

1/2" Torque Wrench
1/2" Breaker Bar
1/2" Ratchet
1/2" Extension
33mm, 1 5/16", or 34mm socket (whatever works for you). I will say that the 34mm socket will work with the 1 5/16" and 33mm nut, but a 33mm socket probably won't work on a 1 5/16" or 34mm nut.

Bad00SS

He just called. its done! checked the TSB on axle nuts. mine were tight. he flushed the rearend fluid and then did a bunch of tight turns in the parking lot to work it into the clutches. the noise is way better I guess. Charged $80 cash for doing it after work yesterday. I'm gonna pick it up on my lunch break.

dmuellenberg

Hopefully that resolves the problem. It did help initially when I was having the problem, but then the noise returned about 6 months later and that is when they replaced the clutch packs (about 7 years and 90k miles ago) and haven't had the problem since.