My step-father has a 71 LeMans Sport convertible and he's pretty sure something broke inside the rearend today. He's was driving along @ 35 mph and he said something went "bang" and the back end "jumped up" and it locked up the rear tires. It wouldn't move forward under it own power so I had to tow him home. Now it is leaking gear oil - we haven't got it up on his lift yet to find out where it's coming from.

I have a couple of questions:

1) Will a 68-72 Chevelle 10 or 12 bolt in or are there differences in the brackets? I know there are some physical differences in the center section and the shape of the diff inspection cover.

2) His BOP 10 bolt is a posi - will the posi unit fit in a Chevelle 10 bolt? I may give him my 10 bolt and find a 12 bolt for my 70 Chevelle.

3) If the Chevelle rearend is a direct bolt-in is there any benefit over a BOP? Or should we just rebuild what he has? Never rebuilt one yet, but we have pretty much everything we need tool-wise, plus he's a 30-year
machine repair-man.

4) Any other ideas/suggestions I might not have thought of...?

Thanks in advance for your help.

Eric

the chevelle rear will bolt right in. The posi unit in the BOP rear has cones that can wear out - the chevelle posi unit does not. Otherwise, they interchange.

I would first figure out the damage.....search this forum for all the info you will need to rebuild, although gear oil leaking out does not sound good, unless it just punched a hole in the cover......BOP & Chevy internals are NOT interchangeable items.....g.

Ive got a Olds 12 bolt for sale. http://www.naxja.org/forum/images/smilies/anon.gif

I suggest looking at the BOP one to see what's wrong with it first, and go from there. If its going to require a complete rebuild, id swap em.

That should be a 8.5" rear in the Pontiac if it is then anything less than a 12 bolt chevy will be going down hill. Non of the parts interchange between the Chevy 8.2" and the Corporate 8.5"

I just finished rebuilding my 8.2 BOP in my Chevelle. (I was strapped for cash). Parts are a bit harder to find, although, they are obtainable. If the current rear is ruined, I would at least look at swapping out to a different rear with cheaper, and more plentiful parts. The 8.2 BOP bolted right up in my 65 wagon.

Rob

Well, Dad got it up on the lift today and the diagnosis is terminal... something in the posi unit gave up and and got under the ring gear and exploded the bottom out of the diff case. He said the hole was big enough to stick his fist in. So, now he's looking for a complete rearend. He's got a 10 to 1 455 with edelbrock RPM cam so he'll probably be looking for a 12 bolt. Bummer about the whole thing is he just bought that rear a couple of years ago.

Besides, how "sad" is it to say you exploded your rearend cruising at 35 mph. It would have been much more dramatic to say he had staged and left the line at 4000 rpm when it broke. LOL.

Thanks for the input - I'll let him kow what to look for.

He probably lost the cross shaft, it backed out and whacked the pinion. I've been there, done that, but was able to limp home, weld the cross shaft in place, and drive it until I found a replacement rear. The little retainer bolt sometimes breaks, allowing the shaft to slide out like that. Not a whole lot else in there to do stuff like that, especially while cruising. Nothing wrong with the BOP 10 bolt, it has bolt in axles and a 27 spline pinion, so it's a bit stronger than a Chevy 10 bolt, until you get up into the 8.5". And for the '71, it's most likely going to be an 8.2" BOP, not the 8.5".

i posted on the buick board but yeah they will interchange . you want a 64-67 bop though cause you cant find parts for a 68-70. as for strength the 8.2 bop is much stronger than the c clip chevy.