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Technical C-4 transmission kickdown shaft play

Discussion in 'Traditional Hot Rods' started by studebakerhawk, Aug 3, 2025.

  1. studebakerhawk
    Joined: Apr 29, 2010
    Posts: 59

    studebakerhawk
    Member
    from Colorado

    I'm building a 37 Ford coupe with a 331 stroker and C-4. I had the transmission build by a local shop and installed it -- only to find out later that with a floor shifter the selector lever must point up and with column shift it must point down. I got it all installed in the car and then discovered my selector was down and I need up. Got the shaft loose, rotated it and now I'm putting it all back together. With the nut on the kickdown shaft tight I have considerably more play in and out on the kickdown shaft than I think I should have. I would rather fix this now with the pan and valve body (and wishbone) already down than to have to chase a leak once the car is completed. how much play is too much ?
     
  2. jaracer
    Joined: Oct 4, 2008
    Posts: 3,017

    jaracer
    ALLIANCE MEMBER

    I didn't think you could just rotate the selector lever. In my mind that will put the part that moves the manual valve in the wrong position.
     
  3. studebakerhawk
    Joined: Apr 29, 2010
    Posts: 59

    studebakerhawk
    Member
    from Colorado

    The selector fits into the part that works the innards of the transmission in two positions -- up and down with a 7/8 wrench sized nut -- and the kickdown shaft fits inside the selector shaft -- with a nut and washer that hold in the o ring and keep the kickdown shaft inside the hollow selector shaft. my issue / question is how much in and out play the kickdown shaft should have. I seem to be able to move the kickdown shaft in and out almost a 16th of an inch
     
  4. saltflats
    Joined: Aug 14, 2007
    Posts: 13,473

    saltflats
    Member
    from Missouri

    There needs to be a little of in and out movement.
    I think there is 2 different length shift shaft and kickdown shafts. If someone install the shorter shift shaft and the longer kickdown shaft it will not work.
     
  5. studebakerhawk
    Joined: Apr 29, 2010
    Posts: 59

    studebakerhawk
    Member
    from Colorado

    I did swap the selector shaft because the one that was on the transmission in the car had a 2 inch deep zig zag in the lever and when flipped over it would have ended up nearly an inch into the floor past the transmission tunnel hole. The other shaft only zig zagged a half inch and ends up still inside the hole instead of needing the floor and transmission tunnel re-worked. it does seem like the nut and washer bottom out on the kickdown shaft before the washer makes contact with the hollow selector shaft. It looked like the hollow selector shaft was the same size on the two selectors - if they are different it must be so slight that it can't be seen --- and the excess play seems to be in that too slight to be seen ball park -- not a huge "thats not gonna work" difference just a "hmm thats quite a bit of play" difference. I'll check into it, thanks
     
  6. Kevin Ardinger
    Joined: Aug 31, 2019
    Posts: 1,028

    Kevin Ardinger
    Member

    A 1/16 is nothing. That would be normal. Depending on what year your transmission it is, that manual valve is going to be super critical! You need to make sure the detents lineup with your column shifter!
     
  7. deathrowdave
    Joined: May 27, 2014
    Posts: 5,009

    deathrowdave
    ALLIANCE MEMBER
    from NKy

    It’s been a while , but I have rebuilt a few of these over the years . Best as I can recall the valve body has to be dropped to swap Dow to up shift lever . Up was the shorter parts Down was the longer parts . The shaft is sealed by an oring as best as I recall also . Moving in and out a small amount will not cause a leak issue
     

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