Topic: Rear end repair - Advice & opinion needed
in Forum: C3 Driveline Components
I just brought my 81 in for its springtime maintainence. I had a slight whine out of the rear last year. My guys told me not to worry about it until its gets worse. Anyway, its worse and they told me to worry about it. I have to get it looked at and repaired. My friends at the performance center wont touch it. They think it needs bearings all around.
A little bit about the car. It has 64k on the clock, the car is meticualasly maintained. Has some minor tweeks - Edlebrock intake, hiflow exhaust, B&M shift kit and a 2000 stall converter.
Heres my questions
What is the typical problem with something like this?
As long as they are going to be in there, is there anything else that should be done as long as its going to be repaired?
Any idea on cost?
Heres my big question(s) - does any one know the stock rear ratio for an 81 automatic? I heard everything from 2:73 to 3:08. I'd like to have the car jump alittle better off the line but I dont want to sacrifice my hiway driving which I do alot of. I dont race the car. So, should I change the gears? if yes what ratios do you recommend....
And once again how bad will all this brealk the bank?
ANy one know anyone in NJ that does this work?
THANKS!! Kevin..
2.73 or 3.08 depends on the transmission installed. Could be either one. One was for standard, the other for automatic.
If you are happy with the system the way it is, there is no need to change gears. If you go to a higher ratio, the top end and fuel mileage will drop, and acelleration will go up. It's a trade off, and depends on what you want the car to do. Based on your statement my guess would be you want to keep the original gears.
As far as the cost goes, it depends on what is actually creating the noise. You have a HUGE range you are looking at. If you do need to get inside the rear diff, changing ratios could increase your cost quite a bit.
If cost is not an option and you want the best of both worlds, install an automatic with an overdrive. The THM200r4 or THM 700r4 will do the job. Then go with a 3.55 gear set. It will get more acelleration off the line, and improve highway mileage. But that's a lot of cash and work.
Kevin,
A friend was very happy with the work done @ http://www.nostalgiamotors.com/ in Boonton, or you can PM Warbird. He has had a lot of work done at a shop in Layton (Sussex County).
Good luck,
Anthony

Moderator

In '81, the only ratio available(factory) for the auto trans was 2.87.1
Joel Adams
C3VR Lifetime Member #56
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Just a thought but, have you checked your fluids?
A couple years ago I swapped out the 2.72 diff on my '81 for a 3.08 diff out of an '80. Made a slight improvement on take off and didn't really affect fuel economy.
Here are the I.D. markings that tell which axle ratio was originally inside for 1981.
2.87 w/AT.....OJ
2.72 w/MT.....OK
Have you ever changed the gear oil in the rear end? Try that first and see if the noise changes or goes away.
Sarge
TKO500 5 spd.
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Born 8/1981
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Friends of mine had similiar noise in thier diff. Tried everything to calm noise. Went to three different shops with no help. Called a Vette repair shop in Detroit, they told them to have the posi clutches looked at. They had the posi checked, found the clutches worn aand had them repaired. No noise. I think the repair cost them about 600 bucks. I hope this helps.
Jim