12 bolt Olds Rear Question

Discussion in 'Got gears?' started by Steve Craig, Oct 8, 2004.

  1. Steve Craig

    Steve Craig Gold Level Contributor

    Looking at a rear end from an A-body Cutlass convertible.
    Vendor not too sure what he has, neither am I.
    Looks like 8.5 housing with 12 bolts holding the cover.
    The 12 bolts indicate anything other than a standard open rear?
     
  2. 71GS455

    71GS455 Best Package Wins!

    I think that's referred to as a "Type O" rear???

    If that's the case, it's 10 bolt guts (not sure if they are unique or corporate) in a 12 bolt cover housing. They're tough to get parts for. Is the ring gear held on with 10 or 12 bolts?
     
  3. Steve Craig

    Steve Craig Gold Level Contributor

    Didn't get a chance to remove the cover.
    Was out gathering a few small pieces for my own car & almost tripped over this rear.
    I've read some discussion here about " some " Canadian GS cars had the 12 bolt posi set-up. Thinking maybe this might be one, only in an Olds.
    Will get back next week, what should I be looking for?
    I can get the axle number if still legible, possibly the VIN on the car will help.
     
  4. gotbuick

    gotbuick What, me worry?


    I'll add what I know. The "O"lds 12 bolts are stonger than an 8.2 10 bolt, but about on par with the 8.5 10 bolt.

    That's about all I know...period. :3gears:
     
  5. 71GS455

    71GS455 Best Package Wins!

    Dang, that's more than most people give you credit for :bglasses:

    I think one of the other problems with that rear is parts availability from the aftermarket - little to none.

    The 12 bolts that the Maple Leaf Buicks got was a Chev 12 bolt.
     
  6. GStage1

    GStage1 Always looking for parts!

    Just leave that 12 bolt Olds where it is. Those were made from 65-70 and they are only worth something to an Olds purist. They are 12 bolt covers on a 10 bolt differential case. Parts are hard to find and expensive.

    Your best bet is the 71-2 corporate 8.5" rear found in Skylark and Cutlass models. Since you have a 71 you will have that rear. You can use the posi section from any GM truck, van, car from 71-88 which have 10 bolt, 8.5" rears and many of the 80-88 GM full size wagons will have a posi set-up.
     
  7. mrBOP

    mrBOP newbie

    If the cover is round and dont have a inverted "V" on it it is an Olds. These are a 8.3 10 bolt inside of a 12 bolt housing. About as a 8.5 and if it is a posi it is a clutch type (like Chebby).
    Parts you can get are posi unit about $450, axels (dont know price off hand), bearings, gears in 3.42, 3.90, and 4.33 only (that i know of) all brake pieces and cover can be bought.
    I am a Olds purist and wish it was closer to Ohio, Dave
     
  8. quicksabre

    quicksabre Well-Known Member

    Dave,
    Are you looking for one of these Olds rearends? I have one exactly like you described that somehow ended up in my rear diff pile.
     
  9. mrBOP

    mrBOP newbie

    It would kinda be nice to have a spare. Posi? what gears? brake parts? Price?what shape its in?
     
  10. quicksabre

    quicksabre Well-Known Member

    It appears to be a 2.56, open diff, no brake shoes or drums, but complete and functional otherwise. $50.
     
  11. mrBOP

    mrBOP newbie

    Thanks but I have a 3.08 open for parts. I was hoping to get a posi as a back up. But ill look around the Olds community and see if anyone is interested. Iam registered to an Olds site if you would like me to post it over there, Thanks for checking, Dave
     
  12. quicksabre

    quicksabre Well-Known Member

    No problem, it's not going anywhere. I know OEM posis for those are hard to come by. If anyone is interested on the Olds site, let me know. It could be a spare for my 70 Skylark daily driver if nothing else. But if someone actually could use it for a pure Olds application, I could always find another BOP 8.2 or an 8.5" if needed. For now, the Skylark is still running strong at 204,000 miles with its original 8.2".
     

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