buffed1978

I have a 1978 corvette.I have a strange noise comning frome my left rear wheel when you turn the car hard to the left at a low speed like you would be making a left hand turn at a traffic light.the sound is just like a scraping noise.Ihave had the car up on a hoist and cannot see any thing that is loose.Trailing arm bushing looks good wheel bearing look good and the rear end was just rebuilt last year has about 800 miles on it.U joints look good .It does not make any noise while driving the car on the highway at highway speeds .iam lost to what it coudl be the car has 44,000 original miles on it only drivern on nice days in the summer.Thanks Buffed 78

z3man987

THATS EXACTLY WHATS WRONG WITH MINE! i just had u-joints put in and the diff. rebuilt, im lost too. plus this noise has only been happening since i did the rear end work. lemme know if u figure anything out because im stumpped

Rockn-Roll

I'm stumped. But, since both of you have had your diff. rebuilt then my guess would be that the shop didn't include a 4oz tube of the GM limited slip additive to the diff. It should quiet it down some. It should be available at your local parts store. It is GM part number 1052358. I believe some shops just use the generic "limited slip " gear oil, but that doesn't seem to do the trick for Corvettes. I use 4 pts (2 qts) of plain GL5 gear oil (pennzoil if I can get it) and one 4oz tube of additive that lists 1052358 as one of the part numbers. I've heard that some of the part stores carry generic additive, but isn't as potent as the authentic GM part, so use two tubes. With one of the gear oil pumps also available at the parts stores I suck out all the old oil, pump about 1/4 of each quart into the differential so that you have two bottles of gear lube each 3/4 full and squeeze half of the additive into the each bottle and shake them up. This will get the additive spred evenly throughout the differential so you won't have to use a break-in period designed for that purpose. Pump the lube into the differential until it starts to seep out and install the plug.

Give us an update to see if that works. You can view other threads with the same topic using the search feature to look for "limited slip additive".

yogi78

Also check that your parking brake is not dragging on one side. I thought that my posi was chattering but it was only the parking brake not fully releasing.

z3man987

ill give the shop a call and ask what fluid they put in, thanks. my p-brake has been shotty from the get go, perhaps ill inspect that too, thanks to u to

ACECO

Yes, make sure the GM posi additive was used. Eliminated the chattering in my posi right away.

I added two bottles just to be sure. I figured that a little extra couldn't hurt, even if it was $8+ per 4 oz bottle at my local chevy dealer.

Good Luck!

buffed1978

Thanks guys for the help.i will check the parking brake ,The garage that put the rear end in put the additive in but Iam going to get them to drain the rear end and put new oil and slip additive and see if that makes a difference I will let you know Thanks Buffed 78

z3man987

yea im guessing the problem is the fluid in mine. looked up that need limited slip fluid and the GM additive, thinking the place just pumped in some 90w or something like that. taking it back tomm. to swap it out and ill let u know the results.