[Shattered]

I know this problem has been talked about, but I can't remember where it was My car is an '08 6m, Z51, NPP exhaust, other than that it's a basic coupe. The problem is a clunking noise while turning the wheel all the way. This only happens when going slow like into of out of a parking spot. It sounds like 4wd pickups I've driven. I don't know if it's in the front end or the rear, it's hard to tell.
Any help would be appreciated, thanks in advance.

[fishslayer143@yahoo.com]

its probably the Posi-Trac Clutches chattering at low speed turns.. replace the differential oil and use the friction modifier additive that goes in it. .

[Shattered]

Originally Posted by fishslayer143@yahoo.com

its probably the Posi-Trac Clutches chattering at low speed turns.. replace the differential oil and use the friction modifier additive that goes in it. .

Thanks fish, I'll try that. Is the additive a dealer only item? Does it take standard diff. oil like a 90 weight, or is it something else? Thanks

[Ragtop 99]

In the cold weather the front wheels will skip across the pavement in hard turns at parking lot speeds, especially on hard runflats. it feels like it is clunking.

If you think it is the differential, The fluid specs are in the owners manual. If you need the additive, it is generally a dealer item. Some of the fluids now come with it.

[Shattered]

Originally Posted by Ragtop 99

In the cold weather the front wheels will skip across the pavement in hard turns at parking lot speeds, especially on hard runflats. it feels like it is clunking.

If you think it is the differential, The fluid specs are in the owners manual. If you need the additive, it is generally a dealer item. Some of the fluids now come with it.

Thanks for responding Ragtop. What you say makes sense, but this happens in all temperatures, so I'm confused. I don't know if it's the diff., I'm just asking for opinions. Fish suggested it may be the diff., but the car only has 10.5k miles. Did GM have a problem with '08's?

[fishslayer143@yahoo.com]

Shattered , there is a TSB on the differential chatter on some C6 s . stop by your dealer, your car may be included, and they will do it

[Ragtop 99]

Originally Posted by Shattered

Thanks for responding Ragtop. What you say makes sense, but this happens in all temperatures, so I'm confused. I don't know if it's the diff., I'm just asking for opinions. Fish suggested it may be the diff., but the car only has 10.5k miles. Did GM have a problem with '08's?

No problem that I'm aware of. I've in parking lot at work it occasionally happens in cold weather when the tires are cold or in warm weather if there are little rocks (e.g. BB size) on the pavement.

If it is happening all the time, I'd swap the fluid.

[Ragtop 99]

Originally Posted by fishslayer143@yahoo.com

Shattered , there is a TSB on the differential chatter on some C6 s . stop by your dealer, your car may be included, and they will do it

Not sure if this the latest version, but it superseded a prior version.

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.

[Shattered]

Thanks again fish and Ragtop. That TSB is very detailed and helpful. I bought the car new in NJ. in July of '08, but I have been living in Illinois for almost 3yrs., and there are a few dealers nearby. I just need to find one I can trust! LOL