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10 bolt rear question

Discussion in 'The Hokey Ass Message Board' started by ArtGeco, Jul 14, 2010.

  1. ArtGeco
    Joined: Apr 6, 2005
    Posts: 759

    ArtGeco
    Member
    from Miami

    I have a rear end for sale and
    somebody asked if it's a 7.5" or 8".
    What am I measuring? Can I determine this
    without cracking the differential cover?
     
  2. ArtGeco
    Joined: Apr 6, 2005
    Posts: 759

    ArtGeco
    Member
    from Miami

  3. hotrodpodo
    Joined: Jun 28, 2006
    Posts: 1,301

    hotrodpodo
    Member

    The 7.5" and 8.2" refer to the diameter of the ring gear.
     
  4. Larry T
    Joined: Nov 24, 2004
    Posts: 7,875

    Larry T
    Member

    I believe the 7.5, the 8.2, and the 8.5 10 bolts all used different covers. You might look at the Richmond gear catalog/website to see what they look like.
    Larry T
     

  5. The 7.5 and 7.85 were the small ones used in Camaros, 80s Monte Carlos and S-10s, very small cover and tubes. The 8.2 was used between I believe 64-72(early) and 73-81(later) and the 8.5 is a newer design I think, other oppinions ??
     
  6. HEATHEN
    Joined: Nov 22, 2005
    Posts: 8,560

    HEATHEN
    Member
    from SIDNEY, NY

    Cover shapes----7.5 looks like a circle with squared off corners, 8.2 looks like a circle with a concave cutout on each side, and 8.5 just looks like a circle.
     
  7. Larry T
    Joined: Nov 24, 2004
    Posts: 7,875

    Larry T
    Member

    There were also a couple of different 8.2 10 bolts. The "standard" Chevrolet type, a different BOP style, and even a 10 bolt ring gear type with a 12 bolt cover. Makes things real interesting sometimes.
    Larry T
     
  8. Larry T
    Joined: Nov 24, 2004
    Posts: 7,875

    Larry T
    Member

  9. The BOP are Borg Warner and thier 10 and 12 bolt version both had a odd 10 bolt cover, semi-circle with cutouts on each side.
     
  10. Nice link by the way Larry.
     
  11. Mr48chev
    Joined: Dec 28, 2007
    Posts: 33,861

    Mr48chev
    ALLIANCE MEMBER

    As I wouldn't even consider buying a ten bolt without pulling the cover, why don't you pop the cover off of it, measure the ring gear and make sure that the rear end is in first rate shape before you sell it. I've looked at too many of them where the pin that holds the spiders in is loose in the housing.

    That will let you know what gear ratio you have too and that could make a big difference in price as some are a lot more popular than others.
     
  12. Larry T
    Joined: Nov 24, 2004
    Posts: 7,875

    Larry T
    Member

    If you'll pop the cover and look, the 8.2 uses 3/8 standard bolts on the ring gear. The 8.5 uses larger metric left handed bolts (at least I think all of them do).
    OK. Just looked at the link and that's gotta be right.
    Larry T
     
  13. Metric? Really? In 1972? When did GM start using metric bolts?
     
  14. Larry T
    Joined: Nov 24, 2004
    Posts: 7,875

    Larry T
    Member

    I don't know, but I looked at the replacement gears and they are the same for 70-96 8.5 rearends. I know the newer 8.5s are Metric left hand threads.
    Larry T



    Looks like I'm wrong again(not the first time, won't be the last). Mr. Gasket lists them like this:

    GM 10-Bolt, 8.5'' ring gear (ex. O axle), 7/16''-20 x 7/8'' LH, 10/pkg
    Stock Length Ring Gear Bolts


    Scuze me while I go look at a couple of rearends I have torn apart in the shop.




    OK, went and looked, the stock lefthanded bolts have a M in the middle. I always assumed for metric, 19MM socket fits them but so does a 3/4". Never too old to learn.
     

    Attached Files:

    Last edited: Jul 16, 2010
  15. OK Thanks Larry.
     
  16. Oh...and if you convert 3/4" you get 19.05mm....which would explain why a 19mm socket will work on a 3/4" bolt head....only 0.05mm difference.
     

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