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Technical Help identifying rearend?

Discussion in 'Traditional Customs' started by Dad Was A Racer, Nov 11, 2018.

  1. Dad Was A Racer
    Joined: Oct 7, 2014
    Posts: 138

    Dad Was A Racer
    ALLIANCE MEMBER

    Can somebody help me identify this rearend? It’s a 10 bolt in a 1956 Olds Super 88 but does not appear to be the factory unit as the numbers don’t match the service manual.
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  2. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    56sedandelivery
    Member Emeritus

    37-56 Olds/Pont. I am Butch/56sedandelivery.
     
  3. Dad Was A Racer
    Joined: Oct 7, 2014
    Posts: 138

    Dad Was A Racer
    ALLIANCE MEMBER

    To clarify a little bit, AFAIK the pumpkin was original to the car (60,000 mile survivor), but the service manual says that the factory designator numbers were either 6, 8, 9 or 0. This one has a plain as day 7 on the case, so I'm stumped. I don't know if this is a pumpkin from another year (assuming it's an Olds) or what?

    Of course I plan to crack it open before running it, but I would still like to know what it's from, etc.
     
  4. F&J
    Joined: Apr 5, 2007
    Posts: 13,222

    F&J
    Member

    I know that Olds rears I have here.....54,55,56 have date codes on the center section. If I think of it tomorrow I will go take a pic of the 54 code I saw.

    .
     

  5. squirrel
    Joined: Sep 23, 2004
    Posts: 55,933

    squirrel
    Member

    is the factory designator number you're referring to, a stamped number? maybe you could take a pic of the book you read that from, so we can see what they're talking about.

    you can also count turns to figure out the gear ratio, but if you're going to pull the pumpkin out, you can find more info stamped on the ring gear, and you can count teeth, etc.
     
  6. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    56sedandelivery
    Member Emeritus

    I think "most" of these were 3.64:1 or 3.90:1 gear ratio. Been a while for me however. I am Butch/56sedandelivery.
     
  7. Dad Was A Racer
    Joined: Oct 7, 2014
    Posts: 138

    Dad Was A Racer
    ALLIANCE MEMBER

    Here's what the '56 book says....
     

    Attached Files:

    squirrel likes this.
  8. F&J
    Joined: Apr 5, 2007
    Posts: 13,222

    F&J
    Member

    The pic you posted in post #1, you show a "casted" number 7, but the chart in your book states "stamped" number, and it is on the lower square shaped boss, as shown in that book info picture.

    .
     
  9. squirrel
    Joined: Sep 23, 2004
    Posts: 55,933

    squirrel
    Member

    yup, clean off the boss, look for the number. Don't be confused by cast numbers, when you're looking for stamped numbers. It's a whole different thing.
     
  10. Dad Was A Racer
    Joined: Oct 7, 2014
    Posts: 138

    Dad Was A Racer
    ALLIANCE MEMBER

    Exactly, which is why I'm wondering if it's not a non-factory pumpkin that was swapped later in life? I have no idea if another GM 10-bolt (from a Chevrolet?) would mate up to the factory axel housing. From the best I can tell, the axel housing is the original, based on the parking brake, etc. but as you can see in the photos, the pumpkin is painted a reddish-orange and has the "wrong" markings...
     
  11. squirrel
    Joined: Sep 23, 2004
    Posts: 55,933

    squirrel
    Member

    Chevy stuff is completely different.

    Look for the stamped number. there is nothing about what you've shown us, that makes it look like it's not original.
     
  12. 302GMC
    Joined: Dec 15, 2005
    Posts: 7,856

    302GMC
    Member
    from Idaho

    That's factory red oxide prime the factory used. Many GM cars & trucks used the coating.
     
  13. Like Butch said.....37-56 Olds/Pontiac. If you can't find the number in your Olds book, look in a Pontiac book.
     
  14. Dad Was A Racer
    Joined: Oct 7, 2014
    Posts: 138

    Dad Was A Racer
    ALLIANCE MEMBER

    You guys were right, as usual... I dug through the grease and crap on the bottom of the pumpkin and found the tiny (about 1/4") stamped number 8, which indicates a 3.42:1 gear according to the manual. Thanks for directing me away from the cast numbers, etc.
     
  15. flatheadgary
    Joined: Jul 17, 2007
    Posts: 1,012

    flatheadgary
    Member
    from boron,ca

    i have that same rear end in my fed. mine has a m/t mag third member.
     
  16. Dad Was A Racer
    Joined: Oct 7, 2014
    Posts: 138

    Dad Was A Racer
    ALLIANCE MEMBER

    Without pictures, it didn't happen :)
     
  17. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    56sedandelivery
    Member Emeritus

    A LOT of Junior Fuel FED's, and even some lesser classes, used the 37-56 Olds/Pont rear ends. They were roughly the same weight as a Tri-Five Chevrolet rear ends, but a lot stronger. As far far as your own personal rear end goes, it very well could have been replaced due to breakage, or to a need for a better ratio. I think the 10 spline axles/side gears were what held it back; even though Mickey Thompson tried to do his part. That, and lack of a Posi-Traction/spool, for them.
    I am Butch/56sedandelivery.
     
  18. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 8,588

    junkyardjeff
    Member

    You might have one from a manual trans,I had a few 53 to 56s that had hydramatics and they has the 3.23 gears.
     

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