User 2623

Thanks for the heads up... I will use the your terminology to explain the clunking. Perhaps this will better focus the tech. Notably this was the original diagnosis from the Chevy CAC center when I asked the question via email and their response. So I have been pursuing that path with a couple of dealerships. They all seem to knee jerk react to this as this TSB will correct the problem and the fluid change would be the answer even after they experience it.

Joe_G

That is a valid concern for us drag racers. I had a new rear built a while back and it was starting to peg leg on my burnouts....thought I needed a rebuild but tried changing from Royal Purple fluid my shop uses to factory fluid (old type) before I rebuilt it...and sure enough, the peg legging stopped. So you can have too slippery a fluid in there for sure.

2000WS6Vert

I had this done last Saturday along with the axle nut TSB.

The car is quiet, what a difference! I had become accustomed to the the groaning and knocking on accel/decel. Now.....it's all gone. No more noises!!!

djgrelli

The dealership changed the fluid in my 05 three different times and the noise seemed to get worse each time. Took it in for the new TSB with the LS Dextron and it stopped almost immediately. It's been about three weeks now and so far so good. The car actually seems a little more quiet now. Yes, they had to order the fluid but it only took a day to come in.

als2052

After the fluid change I am noticing that from a complete stop, if you release the brake and let the car roll forward, it feels like it downshift on its own...???

Bandit1

Greystone

I had the differential chatter for quite a while on my 05 z51. I took it in to the dealer last November and had them change the fluid and additive, but it didn't help. I had to store the car for the winter, just took it out for the first time this spring and now the chatter is worse. In addition I now also have a sort of grinding sound when turning the wheel in either direction, at any speed. Is the steering issue related to the differential problem? I'd like to have a better idea what is going on before I take it to the dealer. Especially since my warranty has expired.....

edv2122

Not sure if I got the new lube when I took the car to be serviced for the clunking noise problem but it has not returned.

Yet

C66 Racing

I've never experienced diff chatter in my 02 Z06 (been using aftermarket synthetics since my car had 800 miles on it) so I've never really experienced what many C6 owner's have complained about... until recently. My daily driver is an 06 CTS-V and though I'm not sure how similar the diff is in my CTS-V to the C6, I recently had an axle seal recall done on my CTS-V. As part of this change, the dealership replaced my AMSOIL diff fluid with GM fluid... and I suspect (but don't know) that they did not put in the GM additive. As soon as I turned out of the dealership parking lot I heard an awful grinding, squealing noise coming from the rear. Instantly suspected diff "chatter".

Shortly thereafter I changed my diff fluid back to the AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 I use in my Z06 (and as an oh by the way the diff fluid plug was completely loose). I did several figure 8's to work the new fluid into the diff and the noise went away... for a day or so, then returned. Although I've never needed AMSOIL Slip-Lock Differential Additive with the AMSOIL Severe Gear as this fluid comes with friction modifier already in it, I considered adding a bottle but didn't have one. So I drove my car for a few more days and the noise went away and has stayed away for about a month now. I suspect that it took longer than I expected to really work the AMSOIL fluid into the diff clutch packs.

In your case, it sounds like your diff fluid has drained out of the clutch packs over the winter. Two suggestions. One - go do a bunch of figure eights to see if you can work the fluid back into the clutch packs. If that doesn't work, consider replacing your fluid with the AMSOIL Severe Gear 75w90 and one bottle of the additive. This approach seems to work very well with quieting the C6 diff.

fast05

The new gear oil works fine for getting rid of the grabbing noise in the rear on turns. It is worse in the Z06 but In some cases it needs to be done twice. Followed by figure 8's in the parking lot to work in the new fluid. You should probably get use to doing it every 15,000 miles the same thing happens to the transfer case fluid in the awd S10 Blazer's and Bravada's. I posted the bulletin on my blog. http://corvettebible.wordpress.com/2...rential-fluid/

Jeff

I had the new LS dif fluid installed about 2 months ago under warranty. The noise prior to the change out was so bad you could feel it when backing out of the garage. Afterwards the noise is gone. If the warranty was over I would change to AMSOil.

cmamich

Had the oil changed out today under warranty, sound is completely gone and shifts are noticably smoother ---- I guess the clunkyness was the diff.... I'm thrilled car drives completely different!

DarkMastyr

Had mine done yesterday. Fixed the chatter and clunk.

Just 4 2

My C5 has a clunk ,sounds like a u joint , wonder if this is the fix ?

nowheelie

While passing through the auto store I noticed

mobil1 LS75w90

...diff oil on the shelf. Has anyone had any experience with this >without< adding any gm ltd fluid?

As many have mentioned, finding 2qts of the gm ls oil is entertaining at best, and I could go with another (amsoil, mobil, royal) for the next longest while.

VET4LES

The dealer changed mine a few months ago and so far so good.

Not Paid 4

Here Here

wbear

Well pricing has changed for the GM Dexron LS.

My GM dealer now says it retails for $20.38/QT and my cost is $15.29/QT.
Since the additive no longer has to be purchased I guess its not too bad.

When chattering starts in my car I will give it a try.

SnowyATX

My '08 built in Oct '07 started (@ 5K miles) the chatter/clunking on tight turns when leaving the parking garage when the diff we relatively cool. Doesn't do it when fully up to temp.

Last night I swapped the oil (forget going to the dealer for something so simple as they'll cause a bigger problem in the process). I "think" it solved the problem. Today I didn't hear the noise and we'll see if it is gone tomorrow as well.

As a side note, damn these C6 mufflers get in the way of the oil change. I like the C5 muffler positions better.

I ended up paying $17.32/qt for mine.

PCMusicGuy

Dropped mine off this morning at 7 and they called me at 10:30 to say it was ready. It's nice and quite now. The real test will be tomorrow morning to see if it's completely gone.