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Technical Ford Flathead Transmission gear ratios

Discussion in 'Traditional Hot Rods' started by bustingear, Apr 4, 2025.

  1. bustingear
    Joined: Oct 29, 2002
    Posts: 2,353

    bustingear
    Member

    I know it is a Ford open drive post 1939 with the desireable large double detent shift tower but I am trying to find out the 1st, 2nd ,and 3rd gear ratios. Anyone close to these?
    Number on the base rear case 78-7006
    Number on Shift Tower 81A-7222B
    Serial number on upper bell area 799C-I 906942

    Thanks
     
  2. Moriarity
    Joined: Apr 11, 2001
    Posts: 37,521

    Moriarity
    SUPER MODERATOR
    Staff Member

    High gear will always be 1:1. the only way to tell the rest is to turn the input and count rotation on the output or remove the cover and count teeth
     
  3. bustingear
    Joined: Oct 29, 2002
    Posts: 2,353

    bustingear
    Member

    i have the cover off but there are several gears on the top and several on the bottom. Which ones to count? Thanks
     
  4. wheeltramp brian
    Joined: Jun 11, 2010
    Posts: 3,345

    wheeltramp brian
    Member

    The cluster gear. 17437948941073031886577756896999.jpg 17437949213353325029268958269318.jpg
     
    alchemy likes this.
  5. bustingear
    Joined: Oct 29, 2002
    Posts: 2,353

    bustingear
    Member

    According to the chart i saw on Van Pelt website a 29 tooth cluster gear can either be a 3.520 or a 3.114 depending on a 14 or 15 tooth drive gear??? And if your going after a cluster dont you have to count all four to get it right?
     
  6. bustingear
    Joined: Oct 29, 2002
    Posts: 2,353

    bustingear
    Member

    Any tricks to counting it without taking it apart? Can only see the edge and too greasy to mark?
     
  7. rusty valley
    Joined: Oct 25, 2014
    Posts: 4,340

    rusty valley
    Member

    Dab a rag on a tooth to clean it, then a dot from a paint marker pen. easy peasy
     
    V8-m likes this.
  8. V8-m
    Joined: Jun 11, 2020
    Posts: 277

    V8-m
    Member
    from Alaska

    Exactly like I did.
     
    rusty valley likes this.

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