76 Rear End Problems
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Pro
Joined: Nov 2008
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From: Denham Springs LA
76 Rear End Problems
My 76 Corvette makes a growling type noise in the back of the car (rear end or bearings I guess) after it's been driven a while. It's a deep growling noise and it almost feels like the breaks are grabbing, however, it only does it when I am taking off while turning left or right. When I take off going straight I can just barely hear/feel it.
After the car sits a couple hours and I drive it, it doesn't make any noise until it's been driven a while, like 30 or more miles I guess.
I had the rear end checked, it's full of oil. How can I trouble shoot this problem?
After the car sits a couple hours and I drive it, it doesn't make any noise until it's been driven a while, like 30 or more miles I guess.
I had the rear end checked, it's full of oil. How can I trouble shoot this problem?
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From: Columbia Missouri
Racer
Joined: May 2007
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From: Cherry Hill N.J.
76 Rear End Problem
The condition you describe could be caused by the clutch pack in rear being worn to the point of replacement........or the additive (anti-slip) added to the rear diff has just lost it's effectiveness.
The most cost effective way to test would be to syphon out the old fluid in rear and replace with new oil and additive...If your problems go away "Great", if not your clutch pack is probably causing the noise you describe.....and will have to be replaced.
Saying that, as long as the diff will be out to service, a complete rebuild might be the best way to go...GOOD LUCK
The most cost effective way to test would be to syphon out the old fluid in rear and replace with new oil and additive...If your problems go away "Great", if not your clutch pack is probably causing the noise you describe.....and will have to be replaced.
Saying that, as long as the diff will be out to service, a complete rebuild might be the best way to go...GOOD LUCK
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Joined: Nov 2008
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From: Denham Springs LA
I read on another post someone recommended siphoning the old fluid out, putting in transmission fluid and running for a little while to flush/clean the internals, then siphon and fill with new oil and additive. Any thoughts on this?
When you say to rebuild versus just replacing the clutch pack, what all is involved? What else do you recommend replacing? Bearings, gears, etc?
Thanks
When you say to rebuild versus just replacing the clutch pack, what all is involved? What else do you recommend replacing? Bearings, gears, etc?
Thanks
Thread Starter
Pro
Joined: Nov 2008
Posts: 680
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From: Denham Springs LA
I forgot to mention that when I stopped to turn I could smell burn't oil. Wasn't sure if it was my car someone around me, but now I am thinking it was my car. What would cause the oil to overheat?
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From: Crossville TN
Your differential fluid could be low or old and dried up. Have you checked it lately? If you find it low [or worse], you will want to syphon out what's left and put fresh gear lube in it...along with a tube of the Posi-trac additive (get it at Chevy dealer Parts area). Hopefully, that will solve your problem. If not, pull it and get it rebuilt.
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From: Denham Springs LA
I looked at the differential and yokes last night. No signs of the yokes contacting the case. No signs of contact anywhere that I could find. I do see that there is some oil around the yoke that connects to the transmission drive shaft. I will drain it this weekend and refill it.
It looks like pretty big job to remove the differential.
1. Is there any benefit to removing the cover off the differential to make sure I get all of the old oil out? Is there any sort of cleaner that I could spray or wash the clutches with to give them their best chance at working properly?
2. Can you get the cover off the differential without removing the differential from the car?
It looks like pretty big job to remove the differential.
1. Is there any benefit to removing the cover off the differential to make sure I get all of the old oil out? Is there any sort of cleaner that I could spray or wash the clutches with to give them their best chance at working properly?
2. Can you get the cover off the differential without removing the differential from the car?
Tech Contributor
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From: Connecticut, USA
That era diff has problems associated with soft side yokes, lousy posi clutch setup, and RG bolts that backed out a lot. They can all be corrected better then most will do but you have to pull the diff out.
With that said, I suggest you look over the U-joints and rear bearings if not done already. Posi hammering will show when the diff is hot and when turning from a stop. The RG bolt problem will either lock up the diff or snap off the bolt. Worn side yokes will have more then 050 endplay by hand, over .100 and I would drop the diff.
Unless you have a diff that was tapped for a drain, you'll have to suck out the old oil from the fill hole. Add Lucas 85-140 gear oil and GM limited slip additive and see how it runs.
The cover can be removed in the car but I don't recommend it for anyone except experienced mechanics, It's only held in by the cross member and the front bracket.
If you have a pinion seal leak and worn yokes then remove the diff, look up my threads on the job it has a lot of pictures.
Remember the diff weights 100 lbs so you don't want that dropping on your head.
With that said, I suggest you look over the U-joints and rear bearings if not done already. Posi hammering will show when the diff is hot and when turning from a stop. The RG bolt problem will either lock up the diff or snap off the bolt. Worn side yokes will have more then 050 endplay by hand, over .100 and I would drop the diff.
Unless you have a diff that was tapped for a drain, you'll have to suck out the old oil from the fill hole. Add Lucas 85-140 gear oil and GM limited slip additive and see how it runs.
The cover can be removed in the car but I don't recommend it for anyone except experienced mechanics, It's only held in by the cross member and the front bracket.
If you have a pinion seal leak and worn yokes then remove the diff, look up my threads on the job it has a lot of pictures.
Remember the diff weights 100 lbs so you don't want that dropping on your head.
Last edited by GTR1999; Nov 20, 2008 at 04:48 PM.
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From: Denham Springs LA
That's good stuff. Thank you so much. I will measure the movements at the side yokes this weekend. I will also change the oil and see what happens. There will be lots of praying between now and then. I found your article on rebuilding the rear end and it's excellent. If I have problems after changing the oil, or find excessive clearances, then I will tackle it myself. With that type of walk through I "THINK" I could build a Rolex.
Thanks again, you can't get this kind of information anywhere else. The internet is truly amazing, it's the best forum for exchange of information and ideas ever!
Thanks again, you can't get this kind of information anywhere else. The internet is truly amazing, it's the best forum for exchange of information and ideas ever!
Tech Contributor
Joined: Aug 1999
Posts: 15,175
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From: Connecticut, USA
That's good stuff. Thank you so much. I will measure the movements at the side yokes this weekend. I will also change the oil and see what happens. There will be lots of praying between now and then. I found your article on rebuilding the rear end and it's excellent. If I have problems after changing the oil, or find excessive clearances, then I will tackle it myself. With that type of walk through I "THINK" I could build a Rolex.
Thanks again, you can't get this kind of information anywhere else. The internet is truly amazing, it's the best forum for exchange of information and ideas ever!
Thanks again, you can't get this kind of information anywhere else. The internet is truly amazing, it's the best forum for exchange of information and ideas ever!
If you rebuild it then don't buy into the fiber clutch or heavy posi spring propaganda.
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Joined: Nov 2008
Posts: 680
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From: Denham Springs LA
I would have bet $1000 dollars my rear end was shot. I drove a little while to warm it up, changed the rear end oil and added the posi additive. Worked like a charm. Groans and noises dissappeared. Must be good clean living or just plain lucky, which is a one in a million for me. Thanks for all the advice guys, again the advise on this website was dead on!
