Differential Problem?

[Norseman]

I don't think I've read anything about this before, so if it has already been addressed I apologize.
I have always had a problem with my car lunging after I first start it up and also when turning in a tight circle or just turning sharply or even on occasion not so sharply this is usually accompanied by a grinding sound or a rubbing sound like a tire on the wheel well etc.; it also sometimes sounded like it was coming from the differential; and it had been getting worse.
Well guess what! I took it into my dealer and he said he just got a message on the problem and said it has to do with the differential lube. He said GM use to put a additive into the diff. fluid for the pos-traction but stopped it in the Vette's. Now for the funny part. The only areas where it has been a problem is the Midwest. They still don't put it in anywhere else and not even in the Midwest unless a customer complained! All Corvettes come form the factory without the additive.
Since the mysterious additive has been added to my car the lunging and noise is completely gone! WTF? Why don't they just add it to all the Corvettes destined for the Midwest? Any way I love my car again.

[Tuna]

My 2006 has been treated to the diff lube treatment twice now. The second time, they doubled the amount of additive in the diff - all quiet for now.

[Norseman]

It's really amazing the difference it makes. I just can't believe they don't add it to all the cars. I wonder what it costs them?

[dtammen]

Anyone know if there's a Tech. Memo on this from GM?

[dtammen]

UPDATE: Clunking noise coming from the rear of car is fixed....I think!

I picked car up from dealer this morning and it drives and shifts quietly, just like a brand new one. This is what was done:

• Replaced the axle nuts and retorqued to 160 lb. ft. (per Corporate Bulletin # 07-04-95-001A) Old value was 118 lb. ft.
• Drained rear differential oil and refilled with Dextron LS gear oil 75W-90, P/N 88862625 differential fluid (per Bulletin # 07-04-20-002A)which eliminates the need to add a friction modifier, as called for in the previous Bulletin 07-04-20-002.

Hope some of you that are experiencing similar problems with your '05-'09 Corvettes (and XLR's too), may find this helpful.

[Patrick]

I have to report that I had this checked on my '06 vert, too. I took it to the dealer (they'd sent me a thank you letter for buying from them which included a free oil change & lube), and I asked them to investigate the differential as well. I've also been getting that noise when I do a slow speed curve, backing into a parking space.

I mentioned to the dealer that I heard there was a TSB about this additive that wasn't being put into the rear differential. They checked and found out exactly what Norseman was saying is true. And it was all done under warrantee!

Hats off to Norseman!


-Patrick

[Norseman]

; I'll dirnk to that!

[NORTY]

There have been numerous TSB's, updated TSB's regarding the differential chatter/grinding issue. Mine has been back twice now. First time they added 2 bottles of friction modifier, the last time they used DEXRON LS fluid. All quiet currently. It is not a problem within the Midwest only. It is worldwide.