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question about a ford 9" rear

Discussion in 'The Hokey Ass Message Board' started by shocker998md, Dec 16, 2010.

  1. shocker998md
    Joined: May 17, 2009
    Posts: 878

    shocker998md
    Member

    alright guys im going to just plain ask this question and I feel like a retard for asking it. Im going back home for xmas and a buddy says he has a 9" that is has 3.00 gears and a posi. I would love to pop the carrier out of that axel and put in my truck that is geared with 373's and is an open diff.

    How can a tell if its a posi. thanks guys.

    I dont think it should matter, but the axel with 3.00s came out of a 77 f150 and its a 9" rear, and its hopefully going into a 66 f100 with a 9". The carriers should both interchange right? Im pretty sure the axel from drum to drum is a different size, but the carries change out.
     
  2. Axle spline count is what you need to compare.....
     
  3. BulldawgMusclecars
    Joined: Jul 15, 2010
    Posts: 508

    BulldawgMusclecars
    Member

  4. HOT40ROD
    Joined: Jun 16, 2006
    Posts: 961

    HOT40ROD
    Member
    from Easton, Pa

    A 77 Ford truck rear. It a good chance it has 31 spline axles. If your rear is a 66 It a good chance it has 28 spline axles.
     
  5. As Ratmotor said, to be interchangeable, both axles must be either 28 spline or 31 spline.

    28 spline axle shafts can be ID'd by looking at the center brake hub area; a big rectangular slot in the center usually indicates a 28 spline axle.

    31 spline axles usually have one small center chamferd hole and two outer holes (one on either side of it). Take a look at the pictures below:




    Ford "trac loc" rearends ("posi" is a GM term) have recessed bolt holes on the spool connecting it to the ring gear, 5/8” bolts, and a rough cast appearance.

    Ford open rearends have flat surface around the holes, 3/4" bolts and the spool is smooth.

    Everything you need to know is here: http://www.kevinstang.com/Ninecase.htm
     

    Attached Files:

    Last edited: Dec 16, 2010
  6. shocker998md
    Joined: May 17, 2009
    Posts: 878

    shocker998md
    Member

    thanks for the pictures gary.

    my 66 has the two circles in the axel so its a 31 spline. Im going up to MD in two days so I should know about the other 9" soon.
     
  7. shocker998md
    Joined: May 17, 2009
    Posts: 878

    shocker998md
    Member

    oh yea the posi term, sory the GM came out in me. Im use to talking about the posi in my buick
     
  8. Relic Stew
    Joined: Apr 17, 2005
    Posts: 1,210

    Relic Stew
    Member
    from Wisconsin

    I'm not sure where this info comes from, but I have a half dozen 28 spline 9" rears in my garage with the 3 hole ends. I've rarely ever seen one with the rectangular slot.

    Could be that all the rectangular ones are 28, but the 3 holes doesn't mean 31 spline.
     
  9. As long as you're pulling the 3rd member out, you can tell if it's an LSD by looking. The Ford LSDs were typically closed (can't see any of the internals). If you look and can see all the gears and a cross shaft in there, it's probably an open diff.
     
  10. geage
    Joined: Jan 25, 2008
    Posts: 94

    geage
    Member

    me too,,, 3 holes dont mean squat
     
  11. i think the posi units have a closed carier.. with no holes to see inside.. I think..
     
  12. Relic Stew
    Joined: Apr 17, 2005
    Posts: 1,210

    Relic Stew
    Member
    from Wisconsin

    Like Just Gary said, on a traction-lok the ring gear bolts are countersunk in a raised clutch cover. On an open the bolts are on a machined flat surface.

    [​IMG]

    And the limited slips are known for cracking the clutch cover between those countersunk bolt holes, so be sure to check for that before you get too invested in it.

    [​IMG]
     
    Last edited: Dec 19, 2010
  13. Mark T
    Joined: Feb 19, 2007
    Posts: 2,044

    Mark T
    Member

    If your truck has 28 spline axles and the traction-loc is 31 spline, you can just swap out the 31 spline spider gears with 28 spline gears. While you have it apart you should replace the clutches.
     
  14. shocker998md
    Joined: May 17, 2009
    Posts: 878

    shocker998md
    Member

    when I grab up the axle ill take pictures and do more reading. Im getting it for free so it wont like illl be out anything but time. and i sure do have alot of that
     
  15. mixedupamx
    Joined: Dec 2, 2006
    Posts: 513

    mixedupamx
    Member

    if the 9" still has the ID tag check the first series of #s in the bottom row it will tell you the gear ratio and if there is an "L" in this line it is a limited slip and as far as i know all limited slips are 31 spline
     
  16. Merlin
    Joined: Apr 9, 2005
    Posts: 2,545

    Merlin
    Member
    from Inman, SC

  17. its just semantics, if you say posi everyone should know what you are talking about. The restorers and the dealership parts counter guy have a problem with everyone calling everything by the exact terminology.


    I have a Detroit Locker in mine, I'm not sure what to call it maybe one of you fellas could help me out. :rolleyes:

    Your question isn't dumb and you have good information to go by. As long as the spline count is good you should be good to go.
     
  18. Primered Forever
    Joined: Jul 7, 2008
    Posts: 963

    Primered Forever
    Member
    from Joplin,MO

    There are 28 spline "L" trac locks.
     
  19. aaggie
    Joined: Nov 21, 2009
    Posts: 2,530

    aaggie
    Member

    A quick check without taking it apart is to turn one axle and see if the other side turns in the same direction. If it does you have a "posi" rear end, if it turns opposite direction you don't.
     
  20. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,566

    gimpyshotrods
    ALLIANCE MEMBER

    X2. I own one, and have seen several more.
     
  21. Da Tinman
    Joined: Dec 29, 2005
    Posts: 4,222

    Da Tinman
    Member

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