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Differential Noise


Active Member
Oct 12, 2007
My XLR/V(s)
Blue '05
In both the XLR and Corvette, it is fairly common to hear a thump from the rear-end, usually when backing up. This is the anti-slip mechanism equalizing itself and is not particularly harmful but is very annoying.

They have a solution; replace the fluid in the rear-end with a different formula which does correct the problem.

In addition to this problem, I also developed a whine. I don't think that was related and I haven't heard of others having this problem... we are just special that way. The whine resulted in a replacement of the differential. Guess even expensive cars can have ordinary problems.
Flush and change fluids

My '06 XLR is going in the shop today for the second time to have the differential fluid flushed and changed as I am still getting the clunking noise and jerking when I am turning sharp corners very slowly such as parking or turning into an alley and then a parking pad where the space is really tight. If this doesn't clear up the problem then the next thing will be a replacement. First Robin:patriot:
Differential fluid change

#07-04-20-002A: Rear Axle Clunk and/or Chatter Type Noise on Turns (Drain/Refill Rear Differential Fluid) - (Jan 9, 2008)

Subject:Rear Axle Clunk and/or Chatter Type Noise on Turns (Drain/Refill Rear Differential Fluid)

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).


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


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.


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

  1. 1456286.gif

    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.​

  2. Drain the fluid.
Filling Procedure

  1. 1456295.gif

    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.​

  2. 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


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

88862624 (US-1 Quart)
88862625 (Canada-1 Liter)

Warranty Information

For vehicles repaired under warranty, use:

Labor Operation
Labor Time
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.​


© 2008 General Motors Corporation. All rights reserved.​
Differential Fluid Change

Thanks Bruce, I printed out all eight pages and will take them with me. First Robin:patriot:
Differential Fluid Change

Now that the fluid has been changed twice everything seems to be working like it should. I had it out today with the top down, parked in places where I really had to do sharp turns and no cluncks or noise, just smooth sailing. First Robin:patriot:
Bruce- Do you have any idea if this newer fluid is recommended in older (60's) Corvettes too?
Good question. I think I would use "normal" gear lube, such as GM part# 89021669. It is a 80W-90 GL-5 heavy duty lube and would work well in an older style differential.

Bruce :)
Thanx, Bruce. If only I could find some old whale oil ...

Good question. I think I would use "normal" gear lube, such as GM part# 89021669. It is a 80W-90 GL-5 heavy duty lube and would work well in an older style differential.

Bruce :)
Now that the fluid has been changed twice everything seems to be working like it should. I had it out today with the top down, parked in places where I really had to do sharp turns and no cluncks or noise, just smooth sailing. First Robin:patriot:
Well my problem came back on the trip to Illinois, took it in today for replacements of the insides of the differential. Just got home from looking at the old parts and you could see the problems on them so hopefully tomorrow will see everything put back together. What a hugh job, the wheels come off, the mufflers and exhaust pipes and on and on. I asked my tech if he was going to polish all the parts before he put everything back on so the underneath will look new again. When they put it up in the air I was able to check my tires, time to get new ones, 22,000 miles on the originals which I don't think is bad for high performance tires.:):):)
Just arrived home from picking up "Little Bugger" and everything is working great. Took it on a test drive with the tech and made real sharp, slow turns, into tight parking and no chatter or jerking. Left the DTS to have it washed so I can shuttle people tomorrow to my friends funeral.
I just took my 2008 XLR-V with 6,800 miles on it into the dealership for the second time for the rear end lube change. It still sounds real bad. They are going to completely rebuild the rear end including both clutch packs, bearings, etc. The service manager said they ordered the parts and the factory had 100 rebuild kits in stock. He said having that many in stock sounds like Cadillac/Chevy is prepared to rebuild alot of XLR and Vette rear ends! NOT GOOD!:pat:
I went and picked up the "V" today after a rebuild of the rear end due to clutch chatter. GM has a bulletin about a rebuild kit to replace the clutches, shims, springs, etc. All issues are corrected and drives great!:rocker:
I talked to my tech today and he said that not only did we have to rebuild the rearend with new clutch packs, but the pinion depth was off. What this means is the pattern was running on the toe of the ring gear tooth. He said that made the whinning noise. So he had to reset the pinion depth in the housing to move the pattern to just below the middle of the ring gear tooth. Runs great now!
When I bought my -05 two weeks ago, it had a "rumble" (no popping noises) from the read end when starting from a dead stop directly into a turn - both directions. As soon as you straightened out, no noise. Also no noise when turning while already rolling - Only happens from a dead stop.

They replaced the fluid and added the additive. It still does the same thing until it warms up. Maybe 10 minutes of driving. Then no rumbles - All turns from a dead stop are quiet

What are your thoughts - especially those of you that hve had the issue and have had fluid changes or differential replacements? Again, no popping, jsut a rumble from a dead stop directly into a turn when the fluid is cold.
I put the Dexron LS gear oil in my STS a month ago and it completely stopped the popping noises it was making while backing up. I plan on doing the same on the XLR now that I have a vehicle lift so I can get under it easily. I did find that to this day the dealers do not have the Dexron LS fluid in stock and still use the old gear oil and additive. They have to order it for me so I guess they are not following the service bulletin to use the new fluid.
Thanks Onalaska,

I'll try to track down the dealer's work order and see what parts were used. I noticed the bulletin says "no additive required" with the LS fluid - they told me they put in the additive, so I bet they used the old fluid...
There are 3 issues with the rear ends in these cars. The first is the incorrect posi lube was used in them which causes the rear end to pop when turning. The second issue is the posi clutch packs are wearning out too fast which also causes popping and an increased grinding noise when turning slowly. The third issue is the pinion depth on the pinion gear is set too deep on some units. This caues an odd squeel when turning and excessive heat in the rearend. All are very fixable but the rearend needs to be removed by the tech to really see what is agoing on. I ended up having the clutch packs replaced, the pinion depth reset and new clutch packs installed, all are covered by warranty.:rocker:
Thanks K9husker. Good info. I'll start with the correct fluid and then head down the path that many of you have already "blazed"!
Probably not the right place to post this, update on my XLR, the tech told me this afternoon that instead of replacing the clutches with 8 as was the original, they are now replacing them with six. This is supposed to remedy the jerking when turning into a tight parking place. "Little Bugger" should come home tomorrow morning sometime, they still have to do the alignment.

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