Hi. I just recently purchased a 1970 GS Convertible Clone. -455 Motor , TH400 Tranny It currently has an open end rear and I am looking to replace with a Posi Rear. I have located a rear that appears to be what I need. My questions are as follows: Before I purchase - What are some of things to look for visually? Mechanically? Rear Code stamp important? After I purchase - Some of challenges in swapping out the old? Should I replace other items when doing the rear itself; springs, shocks? Thank you in advance for your thoughts. Steve
Your car is a clone so. Buy an 8.5 corporate rear end. Parts and gear ratios are easy to find. Always replace bearings and seals. The rear will have a different attachment for the drive shaft also easy to find. Make sure its a A body rear end. I believe its like 54 inches between the backing plates. If you want you can buy an after market posi and gear set for your existing axle and have it installed.
Your original rear was a Buick only 8.2 made 1968-70 ( non Canadian). It is not reproduced. Some 3.42 gear sets were reproduced.
I would first ascertain what rear is in the car right now. Is it a 10 bolt? Post some pictures of the rear cover and u-joint to yoke attachment. Probably the best rear for these cars came in the 71-72 Skylark/GS, the 8.5 10 bolt. If that is what you have, knowing that will save you a lot of time and money. The Buick 8.5 10 bolt is a good strong rear, and aftermarket support is excellent. The Buick rear has bolt in axles, so no c clips, a big plus. I replaced my original rear in my 70, when I started racing the car at the track, and I was well into the 12's. The stock Buick 68-70 rear is good and strong, but aftermarket support is nowhere as good as for the 8.5. I used a Buick 8.5 10 bolt out of a 71 GS. I upgraded the axles to 30 spline, and used a new 30 spline Eaton Posi with 3.73's. When it came time to swap rears, I pulled the axles out, wired up the backing plates, and pulled the rear. On the 8.5, I left the axles out so I could simply swap it in, and install the axles with my old backing plates. I didn't need to mess with brake lines, or E Brake cables. Saved a bunch of time.
What type of 10 bolt is what we need to know. That will dictate your choices. Post up a picture of the rear cover and u-joint retention. Then we can go from there.
Looks like the stock 1970 Buick 8.2 10 bolt. From 1968-70, Buick had their own version of the 8.2 10 bolt. Monzaz has performance gears for it. (see post #9) You'll need a posi for it. See Monzaz for that too.
