8.5 Corporate Rear

J

joeskylark

Member
Can someone explain the concept of "GM Corporate" ? What does it mean? I was recently told by a Chevelle guy that all 8.5" rears are "corporate", and have c-clips retaining the axles. He said that the only way to use an 8.5" rear without c-clips is to use aftermarket c-clip eliminators. Are all post 71 10-bolt rears from BOP to Chevrolet the same except for axle and pinion splines? -Thanks
 
Can someone explain the concept of "GM Corporate" ?

that's GM's practice of taking a specific style of doing things or particular engine and using it across all make and model lines regardless of what division it originally came from. the 350 and 305 SBC are the most notorious examples of this but this but the 3.8L v6 is actually a Buick design that traces it's lineage back to the 1961 Buick aluminum v8 215ci.




all 8.5" rears are "corporate", and have c-clips retaining the axles.

definitely not true for all car lines but it might be true for mid-size cars. Buick, Olds and Pontiac each had specific variations on the 8.5" and none of them used the C-clips.

this may only apply to full size cars 1971-1976 though, i'm not sure about the smaller stuff.
 
Re: Corporate 8.5

Mid size meaning the A-bodies ie. Skylark/GS, Lemans/GTO, Cutlass/442 etc? All I want to do is find the least expensive 8.5" rear I can find so that I can rebuild it. The prices are lower, and the availability is greater for 8.5 parts than for 8.2's. I get a lot of replies from Chevelle guys who seem to have 8.5" rears coming out of their rears, but no BPO owners who are willing to part with anything. Any advice?
 
Mid size meaning the A-bodies ie. Skylark/GS, Lemans/GTO, Cutlass/442 etc?

yes, exactly. 'Full Size' would be a B-body like a Le Sabre, a C-body like an Electra or an E-body which for Buick was the Riviera. the Toronado and El Dorado E-bodies were front wheel drive, so they don't apply to our discussion.

i've gotten back to my spreadsheet though and i've verified that Buick, Olds and Pontiac all produced variations on the A-body 8.5". this is true in 1971, 72, 73 and 76, i don't have decoding info for other years. so your best bet is to look under a BOP car from 71 to 77 or so. earlier is more likely to be a brand specific axle as opposed to the brand swapping that GM really started to get into towards the end of the 70s.

axle codes that denote the ring gear size, ratio and brand are normally 3 letters and on the front side of the passenger axle tube. you might have to wire brush and degrime in order to make the stamping out.

look for a 3rd letter of either B, O or P ( duh :clonk:). other codes like W = Warren,MI or K = GM Canada or G = Detroit Gear & Axle or C = Chevrolet are all probably going to be "corporate" designs.




but no BPO owners who are willing to part with anything. Any advice?

have you tried putting up a part wanted request on this message board or over in the classifieds?




The prices are lower, and the availability is greater for 8.5 parts than for 8.2's.

while all of these are true, don't forget that the 8.5" is also stronger and better engineered. it's not a Ford 9", but it's significantly better than the 8.2".
 
Re: Corporate 8.5

Bob- Thanks for the info. I was pretty sure the source was mistaken. He said he was a Pontiac guy though, and he seemed pretty knowledgable. I'll trust your spreadsheet over his word. Thanks again. -Joe :beer2:Happy St. Patty's Day
 
I'll trust your spreadsheet over his word.

actually, most of the decode data on my spreadsheet comes from a differential service manual.





Here's a little help on the bodies.

Bob, did i ever shoot you a copy of my diff decoder spreadsheet?
 
No, I don't believe I have it! Look forward to it:thumbsup:


hah. i was actually thinking you were "rcull" and i was trying to send the sheet too you so you could post it too Reference.

too many damn Bob's running around here. :clonk::bgrin:

anyway, let's see if i can get this too work as an attachment. if not, you'll have to pm me your email address. the board doesn't permit attachments to pm's.


nope, you gotta pm me your email.
 
Last edited:
You must log in or register to reply here.
Back
Top