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1951 Pontiac chieftain rear end ratio

Discussion in 'The Hokey Ass Message Board' started by peeduh, Aug 22, 2016.

  1. peeduh
    Joined: Aug 26, 2007
    Posts: 70

    peeduh
    Member
    from atx

    Hey all, I have a question or would just like some feedback.
    I just did the rotation of the tire and pinion count and I got a real high ratio. Just under 1 & 3/4 rotation of the pinion for one full rotation of the tire. If I'm not mistaken that's about 1:73, right?
    It's original as far as I can tell. The motor and trans will be a Chevy 350 and a bopth400.
    Thoughts or comments

    Sent from my SGH-T999 using The H.A.M.B. mobile app
     
  2. tazareno
    Joined: Jul 21, 2010
    Posts: 49

    tazareno
    Member

  3. tazareno
    Joined: Jul 21, 2010
    Posts: 49

    tazareno
    Member

  4. F&J
    Joined: Apr 5, 2007
    Posts: 13,217

    F&J
    Member

    Get some accurate marks on pinion, tire and ground. One wheel locked, turn other wheel exactly two turns to give the real ratio, in real numbers.

    Use the chart above, to work with how many turns of the pinion: If you got a tick over 4 turns, but nowhere near 4-1/4 turns, the chart says it's 4.1


    if it's more than 3.5 turns, but less than 3-3/4, the chart says it's 3.63

    Always get the slop out of the pinion, before making your marks, and always do two turns on tire. No math needed that way.
    .
     

  5. peeduh
    Joined: Aug 26, 2007
    Posts: 70

    peeduh
    Member
    from atx

    Tazareno
    Hey, thank you for the reply. I do have a 6 stamped on there do I'm assuming it's gonna be the 3:63.
    F&J
    Thank you as well. I'm gonna redo my test tomorrow with one wheel unable to move. My motor and trans and drive shaft are out of the car so it makes it easier.


    I'm understanding that running this rear end with my 350 and th400 will be great since the tranny has an over drive

    Sent from my SGH-T999 using The H.A.M.B. mobile app
     
  6. There's no overdrive built into that transmission, it's a 3 speed with a 1:1 high gear.
     
    gimpyshotrods likes this.
  7. peeduh
    Joined: Aug 26, 2007
    Posts: 70

    peeduh
    Member
    from atx

    Hey, so I checked with the other wheel fixed and sure enough I got 3:63.

    Pocket Nick- you're saying the th400 doesn't have an over drive?

    Sent from my SGH-T999 using The H.A.M.B. mobile app
     
  8. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,898

    gimpyshotrods
    ALLIANCE MEMBER

    The TH400 is a three speed automatic, with a 1:1 top gear.

    It does not have an overdrive.

    For an overdrive you will need a 700R4 or a 20004R.
     
  9. peeduh
    Joined: Aug 26, 2007
    Posts: 70

    peeduh
    Member
    from atx

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