cbgpe

I have been noticing slip/stick type noise on my Z in tight turns. I know some additional rear end friction modifier will "fix" the problem but is anything getting damaged in the interim?
Should I take it in for service right away or wait until the next oil change?

GOLD72

Getting a diff fluid change asap would be the safest approach. I have one friend who has had 9 vettes and 4 or 5 of those had chatter. He believes the chatter will gradually get so bad that even a fluid change will not help. I let mine go a long time and the dealer's fluid change a year ago worked only for a month or so before the chatter came back during the summer worse than ever. Finally I did my own DIY change 3 months ago using AMSOIL Severe Gear with a separate addition of 6oz of the Slip Lock Additive. The effect was immediate and 3 months later on this daily driver it is still quiet. If it will stay quiet for another 3 to 6 months, I will be ready to claim victory. I am hearing some stories that the new Dexron LS fluid (going into the ZR1 & maybe all of the 09 vettes) is now the official recommended fix by GM via the latest TSB. Good luck.

PS: my Z was born 2 years ago today.

Zoxxo

1. No.
2. Wait (unless it really bugs you.)

Seems that most of us just get used to it.

Z//

RichieRichZ06

Here is a copy of the new bulletin where it states to not use the friction modifier with the new fluid. GM just released the new gear oil for the problem. Read.


Document ID# 2048181
2007 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
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.





© Copyright General Motors Corporation. All Rights Reserved.


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

Zoxxo

Excellent! Thanks! (Now let's just hope it works )

Z//

Jimbeaux

This is very helpful information.
Now can someone tell me how to drain the fluid on an 05 without getting it all over the rear leaf spring?
I read somewhere that oils or solvents should not come in contact with it.

GOLD72

I use Reynold's Wrap (alum foil) to wrap around any suspension parts that likely will get wet when I change fluids. Definitely speeds up the post fluid change clean-up. The 99 Honda Accord V6 is the only car I routinely use foil because of the weird angle for the filter mounting.

Jimbeaux

Excellent suggestion! Thank you very much