I just had the rear end fluid changed in my IROC about 2 weeks ago. Just about 2 days ago I started to hear a whiring sound from the rear end. Just took it back to my mechanic who check the fluid level out. He said its full but the fluid is black again. The car probably went over its 20,000mile change recommendation. This is the first change that I have had done since I got the car. So what do u guys think is up? Bearing or gear?? it sounds like gear but Im not too up on axle information.

 

I had the same problem. I changed my diff fluid without adding the GM Limited Slip additive. It whined.

I re-changed it & added 2 little bottles of this GM ADDITIVE. It went away in a day.

Make sure he added it.

 

I was trying to buy that GM additive at the dealer. They were out of it and the tech told me that THEY don't use it anymore anyhow. He said the oils nowadays already have something like it in it.

TRUE?? I'm not thinking so, but it could be.

The rear does whine a bit, but I thought that was just because my sound deadner needed to be removed. I never drove my car before I restored it so I'm not sure how much noise it's supposed to make. I had it all apart and I know it is worn, I just replaced the axles for now. I know I'm losing a little power there. Just waiting until i find a disc rear to POSI-ize

Ever sit in the back of a new ford explorer?, It's not even close to being as loud as that rear-end, but it's there.

 

use the gm additive, nothing else for clutch type posi units

 

ya i asked him today if he put the GM stuff in. he said "um we put an additive in, does the same thing" Im gona go back and say, "um, ya, put this stuff in" I ask for something, i expect to get it...........arg.

 

well, to a point he's right. it's not needed in the new camaro's due to the torsen and it can't be used in trucks. only the corvette needs the additive now. you didn't happen to use synthetic did you?

 

go to a different GM dealer. i know the additive is still avail because i
(A) worked at a GM dealer a few months agoin in the PARTS DEPT
(B) im going to go get some tomm from a bud that works at a pontiac dealer and i checked on it about a month ago.
if all else fails go to a reputible parts place and ask for an additive. a- zone has some but id go to another place first. go to a delco dealer because the are more familiar with GM autos.

 

no i didnt use synthetic.

I can get it at the local chevy dealer, they stock it
The car is really geting loud out back now. Its normal when im on hte gas but once i let off and the RPMs drop there is really loud gear noise. Is that still cause of the lack of the additive??? Keep in mind it made no noise before the lube change..........

 

see if you have enuff room to get the additive in the rear. do that first.
if it is still noisy after you drive it ( a mile or 2) then find yourself a reputable shop that does rear ends. talk to the person there and get their opinion. the clutches in the carrier might be warn or burned up.
do you have the 9 bolt borg or the 10 bolt?
if you have the 10 bolt you can get a replacement carrier at your local speed shop.
if you have the 9 bolt borg drop mileskoolmister a line. you can find his addy on the drivetrain section of the msg board.

 

The additive shouldn't have any effect on straightline driving, it's used to allow the posiunit to spin against itself without chattering..i/e when you're making a turn.

If your rear is whining when driving straight down the road, you should have it diag'ed for bearing or gear issues.

 

why would it start doing this after a lube change????? wouldnt that help the rear out?????

 

ttt

 

That is very odd that the rearend started the problem after the fluid was changed. It would be a big coincidence that it would go bad right when the fluid was changed. The only thing to do is tear down the rearend to see what is wrong. Most shops will charge you an arm and a leg, though. You can get a take-off Torsen posi from SLP for 85 bucks. You can get Motive gears from www.ls1motorsports.com for 175 bucks. <---That's assuming you have a 10-bolt.
BUT, if you have the 9-bolt rear, you might as well buy a complete 10-bolt rear to replace it. The 9-bolt parts are extemely hard to find, and expensive.
-OR-
If your 9-bolt is a 2.77 ratio, I have a posi unit and 2.77 gears, with all the bearings - all in excellent shape. I'd sell it all for 50 bucks shipped to your door.

You need to crawl under the car and see if there are 9 or 10 bolts holding the cover on. Then read the little tag on there, and it will tell if the ratio is 2.77, 3.27, or 3.45.

Post up and let us know.

Jason

 

Hard to find - Nope, not anymore www.9bolt.com
Expensive - That depends on how you look at it.

Miles
www.9bolt.com