Hi all, I have a 68 with an open rear. I can get a posi from a 67 skylark. Do you know if this is a direct swap? Also, what models and years can I do a direct swap with? thank you! matt
if you don't care about originality, you're best bet is to go with a 71-72 10 bolt 8.5" "corporate" rear as parts are plentiful. The 68 GS rear is a weird bird with bearings that are next to impossible to source and prone to failure if driven enough. 69/70 8.2" is a bit better but the 71-72 are much stronger. You could also go with a chevy 12-bolt but the upper control arms and pinion side U-joint are different.
As I remember the 65/67 8.2 are different, hard to get parts for but not as bad as 68/70 8.2. 71/2 8.5 is the best to build.
Thanks for the input! Pardon my ignorance, but what do you mean by corporate? Also, for me, I'm just keeping the interior original. It has a modified 455 from a 72 Buick in it now. I was told it was 400 hp and 500 foot-pounds of torque. How much can the 10 bolt corporate handle? Thank you.
The 68-70 Buick 8.2 is unique to Buick. There is very little aftermarket support for it, and it is more expensive to build. The 64-67 BOP rears are also 8.2 10 bolts, but they are different than the 68-70. Parts for the 64-67 BOP rears are easy to find. Our resident rear gear specialist is Jim Mitchke, his screen name is Monzaz. I believe Jim has found a way to modify the Auburn posi to fit the 68-70 Buick 8.2. I'm not sure about this so you should contact him through the V8 board, or his business. This is his site, www.jdrace.com (looks as if it might be down right now) In 1971 and 72, Buick went to the 8.5 10 bolt, also known as the corporate rear. It is a good strong rear with bolt in axles, in fact all the Buick rears from 64-72 are bolt in axle, no C clips. I have a 1971 8.5 in my car. I have 30 spline Moser axles and a matching Eaton Posi, 3.73 Yukon gears, and a TA Performance rear cover with girdle. It handles the car in my signature with ease, so far.
Thanks! This has been very helpful. I did find this, which they said is a revised auburn. Unfortunately they don't have any more in stock and they don't know when they can get more. Plus you have to buy the pin and ring gear for a total of around $1300.... Yikes. http://www.taperformance.com/proddetail.asp?prod=TA_1780-C
Reach out to Monzaz, he can definitely help you out. I purchased my 8.5 rear from him and have nothing but good things to say about dealings with him. Tony
Thanks for all the help guys. I should probably confirm that I still have the 68 rear in it. I have pics but the image insert icon above is not working with either my phone or the computer.
That, my friend, is a Chevy 12 bolt rear .. now your options are almost limitless .. .. it is also known as the 12 bolt 8.875 passenger car rear. Buick did use this rear but only in 1969 Canada built special / skylark / GS's.
Laughter and Tears of joy! thank you gentlemen for your help! even a blind squirrel finds a nut once in a while! so do all 12 bolts have a 8.875" ring gear and 30 spline axel?
probably 68-72 .. same rear prior to 68 but the "width" - side to side, or more properly backing plate to backing plate - was 1" shorter prior to '68 The only slight downside to this rear is that the axles are retained in the housing with "C" clips where as the Buick rears have the axles retained with bolts. Bolts are better .. .. but this design has been around forever. I've run a "Built" 12-bolt in my GS for 12 or more years with first a 475hp motor and the past 10 years with a 550hp motor. I had it professionally rebuilt using a new Eaton HD posi carrier, Moser axles, new bearings and seals. This was after breaking 2x 8.2 and one 8.5 Buick 10 bolts. I have another that will soon go in the SportWagon which btw, uses the same '68 that I was hoping you didn't have. '68 GS Big Block & Sporty 8.2" rears are slightly different than the 69/70 rears in the outer bearing .. which is prone to failure and basically unavailable anymore. Seriously consider contacting Monzaz for your parts - he's a great guy and supports this site with very helpful info. He could also build your rear for you but you'd have to ship it to him. Being its a 12 bolt chevy rear .. you should have no problem finding a good local shop who can do the build.
Yes all 12 bolt chevy from the factory came with 30 spline c-clip axle shafts. 8.875 ring and pinion. Remember your ring gear has 12 bolts which is what makes it a 12 bolt the cover just happens to match the ring gear bolt count.
