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I have a quick question.I have a 77 nova with a 7.5 open rear end.I have put a 454 in the car and traction is non existent if I try to floor it out of the hole.I have found a 76 nova an 8.5 rear in it and I know that it should swap right in.I believe this 8.5 to be a non posi unit.From what I have read it should have 28 axle splines.If I were to buy this 8.5 and find a posi unit from another 8.5 rear say from a truck is it possible to swap it in?Would it work even if the truck has 30 axle splines?Any help is greatly appreciated.
 

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No truck 8.5" ever came with a "posi" if by that you mean a limited slip differential. All the ones that came with the G80 option code had a Gov-lock. The Gov-lock is the last thing you would want under that car. They do nothing till one tire gets up to about 100rpm faster then the other and at that point they lock solid (often with a bang and sometimes parts launching out the diff cover) just to unlock when wheel speed gets over about 40mph.

I vote that you look for a used diff out of a car or a aftermarket. If you go aftermarket it wouldn't be a bad idea to get a 30-spline diff and new axles to go with it.
 

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since you are going from nova to nova, everything should be the same, however there were some differences that are worth checking to make sure it will fit. measure the distance between the shock mounts on both axles, also make sure your shocks mount in front of the axle or behind (this may sound silly but a friend of mine checked everything except that...) and also check the bolt pattern on the axles so that you dont end up with a different rim bolt pattern front to back. then just buy the gears you want and an eaton or auburn unit. this is not nearly as expensive as it may sound; its more time and labor consuming than anything. contrary to what alot of people may tell you, your 8.5" 10 bolt is an extremely stong rearend. build it right and it can handle anything you throw at it.
 

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one other thing to mention. the driveshafts should be different lenths since the 8.5 pinion is a little longer than the 7.5. but again since both are novas the car with the 8.5 in should have the right lenth shaft. don't forget some quality "j" bolt slapper bars on that thing. there are other traction devises too, but you'll need to use something or you'll have horrendous wheelhop.
 

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You'll probably need a slightly shorter drive shaft. I took one out of a '77 Nova w/7.5", and tried to put it in a '78 Skylark (Nova w/Buick trim) w/8.5", and it was about 1/2"-3/4" too long. Both cars had T-350's.
 

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Junkyard parts that will swap in are from mid-seventies Camaros and Firebirds. Very difficult to find. I was only able to find one that had already been rebuilt. All the yards in Michigan had been picked clean since some of the magazines did stories on how the 8.5 rear end was almost as strong as the twelve bolt. Good Luck! :cool:
 

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'70s Camaro/Firebird rear end housings will not bolt into any year Nova. They are too wide, and the spring spacing is different. Gears and posi units, however, will fit OK.
 
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