I need a rearend BAD for my 78 Grand Prix. I found this rearend, 3.73 posi, but he wants $500 for it. Half the people I talked to say this is a rip off, the other half say its a steal. Which one is it????? The rearend is out of a late 60's Chevelle. The Posi appears to work, since the rearend came from a car that runs high 9's @140+. The gears are a little too steep than what I originally wanted for my Grand Prix, but I guess all that means is that I'll need to get a much larger cam.......which I planned on doing anyways. The other deal is that he is letting me take the rearend for $250 now........and the other 250 later. plus he owns an exhaust shop and is going to weld the new muffler onto our camaro for free besides the cost of pipes, which is like $100 in labor.......so its actuallly like $400 for the rear. What do you guys think?????? I could get a 8.5 inch 10 bolt in the junkyard with no posi and 3.08 gears (which would work PERFECT for my mild cam in the big block caddy, but would work ****ty with a good cam later on) for $150. Opinions???

 

it isn't going to bolt up, you'd have to change all the mounting points and brackets. 500 dollars is a fair price for a 12 bolt posi

 

How many times has the diff run a 9 second pass? They don't last forever at that load...

Has the posi unit been rebuilt? how old are the gears/pinion?

A new Eaton 10 bolt posi unit costs $440, a Richmond gear 3.73 is $165, a rebuild kit with bearings etc... is $80 (all from Summit) and install cost of $100 is less than $800 for a totally new setup.

At $500 you aren't really getting a steal...

 

The 12-bolt is NOT a bolt in. You'll need a kit to bolt it up, new spring perches welded on etc....

If you have the motor to warrant a STRONG rear end ( BTW.....I know PLENTY of guys running the stock 7.5" G-Body rear WELL into the 12's, they only seem to die when you start using slicks and hooking REALLY GOOD ) Go with a Buick GN / T-Type rear. It's a straight bolt in, the only mod needed is to shorten your driveshaft 1".

Try www.turbobuick.com and then check the Turbo Trader link, I see posi 8.5" GN rears for $400-600 all the time.

The ONLY G-Body's to get the stronger 8.5" rear are as follows:

84-87 Olds Hurst Olds and 442
84-87 Buick Grand Nationals and T-Type Turbo cars

HTH
Chris
85 IROC

 

Actually, you don't need to buy an overpriced installation kit, I know of at least 4 of my friends running A/G 8.5inch/12bolts in there G bodies. The only bitch is you have to weld on some new springs mounts using old exhaust pipe, and flex the control arms to fit, then see if you're going to need to drill new holes to position the lower control arms. My friend with the 9 second chevelle ran his rear like this with no swap kit, and I'd say a 1.40 60 ft is good testimony to it working right!

I got a chance to pick up a 10 bolt 3.26 rearend for $50! I think I'm going to take it.
Chris

 

Buy the 8.5, it can be beefed up in the future.

 

Well, now I dont' know WHAT to do......the guy that wants to sell me the 12 bolt really sweatened the deal.............he just custom made a 3inch exhaust for my girflriends camaro today for FREE, and the cars sounds frick'n badass with a hooker aerochamber dual out muffler. He did it for free...........also he's going to give me a set of badass looking rally rims with 275/60/15 tires mounted on it, which are about 28inches tall......that would make the 3.73's more like 3.42's. So hmmmmmmm......I'm thinkinga bout offering him $400.
Chris