Rear Differential
Burning Brakes
Joined: Dec 2005
Posts: 1,179
Likes: 100
From: cranford nj
what kind of noise do you have, my 71 made noises when I turned or started off slow. Drain the rear added new gm fluid and 2 bottles of posi additive went and did some figure 8's no more noise
Melting Slicks
Joined: Jul 2010
Posts: 3,176
Likes: 633
From: perth western australia
Agree with Blue by you , my 77 diff sounded like death warmed up until I replaced the oil with new additive , sounds (banging/grinding ) noises went away and haven't come back.
Thread Starter
Instructor
Joined: Aug 2017
Posts: 115
Likes: 15
From: Lebanon Ohio
It’s the original 3:36 included when I bought the car which had a 3:55 installed. I preferred the 3:36 and just took a chance it would be ok so I changed it whilst doing some clutch work.
The noise sounds like pinion bearing - no howling, just rumble grumble under load and cruise and changes somewhat to a higher frequency when I let off. Push in the clutch and coast and it quiets some but still has that rough unhappy bearing sound.
So fluids are new but... I’m just looking for an answer. The previous owner removed the 3:36 years ago and couldn’t remember what it sounded like. FWIW the ring gear looked great with barely any wear marks at all. The unit probably has about 80000 miles on it.
The noise sounds like pinion bearing - no howling, just rumble grumble under load and cruise and changes somewhat to a higher frequency when I let off. Push in the clutch and coast and it quiets some but still has that rough unhappy bearing sound.
So fluids are new but... I’m just looking for an answer. The previous owner removed the 3:36 years ago and couldn’t remember what it sounded like. FWIW the ring gear looked great with barely any wear marks at all. The unit probably has about 80000 miles on it.
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,986
From: Connecticut, USA
Look on the side of the ring gear for the date code and tooth count. Check to see if they are GM or other. Installing unknown used gears is always a gamble and I know guys that got the R&P from diff sets mixed up and that will also lead to noise issues.
Did you do a pattern check and lash check or just reuse the shims that were in the diff before?
New bearings typically don't go bad unless they were dropped or otherwise damaged, so I would look at the gear set or setup as the issue maybe both.
Did you do a pattern check and lash check or just reuse the shims that were in the diff before?
New bearings typically don't go bad unless they were dropped or otherwise damaged, so I would look at the gear set or setup as the issue maybe both.
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,986
From: Connecticut, USA
ok I misunderstood. Be sure to have the posi checked for any cracks if you get into rebuilding it. It might just be bearings, which USA Timkens are still available for. Good luck
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