I know this has been beaten to death before but here's my question.

I changed the diff fluid with GM 89021677, which is the older style GM lubricant without the additive. I filled it up with 2 quarts and did not put any additive in it.

Is the additive really necessary? If so, can I still add the additive even though I drove a few miles without it? How much additive should be put it in there? Thanks in advance!

Tom

 

Opinions vary on this one but I personally still prefer using the GM Limited Slip additive (only with a fluid that does not include the additive in it that is) when doing a rear fluid change.
You can add the bottle (4 ounces I believe?) after the fact if you want/need but you may have to draw some of the fluid out first (with a simple manual pump) to make room for it.

 

The gm fluid that does not need the additive is part #88862624. I think the older fluid #that you referenced does require it. The gm additive comes in a pre measured bottle, you add the entire bottle. You can still add it after you've driven . I do think its necessary for quiet operation.

 

Oh,,, you will realize your mistake when you make a tight turn, you get popping and chattering from the rear. If you don't run the additive and it doesn't chatter, you either have fluid that already has enough additive or your clutches are shot!

Yes you can add the stuff after the fact if you need to.



BC

 

Thanks for your input. I went ahead and I've added the additive.
What's interesting is that without the additive and the new fluid in, the chattering sound became quieter than with the old fluid in.

But after I added 8oz of the GM additive the sounds went away right away.

The reason why I put 8oz, is because of TSB released by GM.
Thanks!

 

After doing a rear fluid change, going to a large parking lot and doing a few slow speed 'figure 8s' (driving around in circles going left, then doing the same going right) helps distribute everything throughout the clutches and such within the rear as well.






Just so ya know, that additive isn't necessarily a case of 'if a little is good, then more must be better'. Meaning that there is such a thing as having too much of it in there, an excess amount of it can create too much slip and actually prevent both wheels from spinning (or gripping) equally under a burnout or full throttle situation.
I only added one 4 ounce bottle last time I did mine.

 

Here's the TSB; it calls for 8oz. (2 bottles)


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

 

That bulletin has been superceeded by just using the newer fluid, right?

 

I think it has, yes.
But even if using the bulletin shown above, (which can still work) some of it's content is not entirely accurate for every circumstance.
I still believe that two full bottles of additive is just too much in most cases.

 

Yes

 

Drove the car all day today, no problems, no strange sounds, no chattering, spun the tires all the way through 1st... typical C6 Corvette.

Thanks for all the replies.

 

If all is quiet on turns, I would leave alone. If chatter comes back, by all means use the factory fill fluid GM started using with MY2009 which is DEXRON LS or many of us have used AMSOIL Severe Gear with great success. I am surprised you opted to use the older Mr Goodwrench fluid which has not prevented clutch chatter over a great many years. You likely brute forced quieted your diff with the double dose of additive. Its probably okay since it was an operative GM TSB at one time so they must have considered the double dose to be acceptable.

 

Yea... I ordered the old fluid by accident, so I had to put in the additive. My mistake for not clearing that up.

 

I just ordered the Full Synthetic Mobil 1 diff fluid. Do you believe I will need to purchase the additive?

Thanks!

 

Found this on Mobil 1's web site -


Question:
Gear Lube to Use in a Newer Corvette
Does Mobil 1 Synthetic Gear Lube LS 75W-90 meet GM spec #88862624 for Dexron LS 75W-90? Will its use in my C6 2008 Corvette void its warranty?
-- Robert Sullivan, Melbourne, FL
Answer:
No, it does not meet this spec. The GM spec product is designed with a very specific level of limited slip (LS) additive to provide optimum performance for that particular vehicle. Having said that,
Mobil 1 Synthetic Gear Lube LS 75W-90 also contains LS additive and it will provide outstanding protection and performance but it could require more LS additive for this specific application. We recommendation you follow the vehicle manufacturer’s recommendation.

 

Based upon the website's advice, I think you will be okay to add up to a 4oz bottle of additive. Back several years ago prior to the introduction and availability of DEXRON LS, I did a DIY with AMSOIL Severe Gear which already is formulated with slip lock additive. Since I already had a severe chattering problem that a dealer fluid change didn't fix for very long at all, I was desperate since the next course of action for GM was to replace the clutch packs. I added an additional 6oz of additive along with the 2.7 qts of AMSOIL fluid to my 06Z. Worked great and never had a chattering problem since. The current at that time TSB suggested dealers double the additive amount to the standard Mr Goodwrench diff fluid to resolve the chattering problem when doing the fluid change. Hence adding one dose of additive when AMSOIL already included one dose was in effect meeting the existing TSB. Your results may vary.

 

For C6 owners considering AMSOIL as Gold72 mentions above, I do recommend adding one 4 oz bottle of their slip lock additive to the Severe Gear 75w90. Seems to do the trick to prevent diff chatter in the C6 although I've never used extra additive in my 02 Z06.

AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 (Product Code SVGQT)
AMSOIL Slip-Lock Differential Additive (Product Code ADATB)

 

The Mobil 1 LS worked fine in my 04. Later! Frank