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Technical Caddie Hydramatic tech Q

Discussion in 'The Hokey Ass Message Board' started by Speedchop, Oct 26, 2014.

  1. Speedchop
    Joined: Jul 7, 2013
    Posts: 81

    Speedchop
    Member
    from Sweden

    Guys,
    Got a question related to the gearbox behavior in my Cadillac -54. I'm used to the good ol TH350 so this is new to me. Sometimes when my gearbox is shifting up it seems like it skips 3:rd gear. It's not common byt every once in a while it sort of skips 3:rd and goes directly to 4:th. I cannot figure out if there is any logic with load or anything. The gearbox shifts nicely and there are no hard skifts or anything apart from this. Also when coming to a stop it seems like it disengages the drive pretty late, just before coming to a full stop. I can feel it's in gear when braking and then when the engine is about to studder it releases the gear and shifts down to first. I've heard that the HM can be a nightmare to adjust cos of the mechanical control. Any tips or input?

    Thanks/ Speedy
     
  2. Speedchop
    Joined: Jul 7, 2013
    Posts: 81

    Speedchop
    Member
    from Sweden

    Anyone?

    Thanks/ Jonas
     
  3. saltflats
    Joined: Aug 14, 2007
    Posts: 10,609

    saltflats
    Member
    from Missouri

    Have you serviced it?
    Kinda sounds like the governor hanging up. Maybe service it and add some transX.
     
  4. Speedchop
    Joined: Jul 7, 2013
    Posts: 81

    Speedchop
    Member
    from Sweden

    Well, just bought the car but I'm told it's serviced properly. Carb is swapped for a Edelbrock so there is a special linkage. Previous owner struggled with the linkage and had to fab a new carb arm. To my knowledge it only controls kick-down right?

    Thanks/ Jonas
     

  5. saltflats
    Joined: Aug 14, 2007
    Posts: 10,609

    saltflats
    Member
    from Missouri

    It may control throttle pressure also I would have to source out a manual.
     
  6. dan griffin
    Joined: Dec 25, 2009
    Posts: 481

    dan griffin
    Member

    It sounds like the T/V rod is not right. This controls valve body oil presser for load and speed.
     
  7. I have experienced similar behavior in those old hydros as a kid about 50 years ago, but didn't have the sense to figure it out or even worry about it. I think as noted above, they can be a little tempermental about TP adjustments.
     
  8. inline 292
    Joined: Aug 25, 2006
    Posts: 296

    inline 292
    Member

    The throttle linkage on the hydro does what a vac. mod. does on a later design. So, if the ngine load drops at the time it is changing gears, it will sense this & skip a gear. same thing you do without thinking when driving a manual gearbox & cresting a hill at a shift point or letting up on the throttle due to a car cutting in front of you. Nothing scary about experimenting with the linkage. Just go slowly, maybe a 1/2 turn at a time & then road test it. Coming to a stop, it never does disengage as you say. It downshifts & the 'disengagement part' is due to the fluid coupling in front of the gearbox.
     
  9. Poncho60
    Joined: Jan 23, 2011
    Posts: 242

    Poncho60
    Member
    from N Illinois

    The rod from the carb to the trans is what controls its performance. If you could get your hands on the service manual for your car or perhaps someone could copy that section and supply it to you it might be a lot better than guessing what's going on. The dual coupling hydro on my 60 Pontiac uses the same kind of trans control and the TV rod adjustment is critical to the trans performance. Not sure the carb swap was the best idea as these are not really set up for this kind of trans control. Good luck!
     
    loudbang likes this.
  10. Speedchop
    Joined: Jul 7, 2013
    Posts: 81

    Speedchop
    Member
    from Sweden

    Thanks Guys! Much appreciated input. I'll read up on the adjustment procedure. Noted about the carb.. It does have a special linkage and I assume that the total stroke is the same as the original carb but its worth checking.

    Thanks/ Jonas


    Posted using the Full Custom H.A.M.B. App!
     
  11. telekenfun
    Joined: Mar 9, 2010
    Posts: 250

    telekenfun
    Member

    Let me refer you to posts I made to "Fender 1325" posts #39 &#40 where I describe Motors Manual adjustment procedures for your Caddy's transmission.
    Best Regards and good luck with all your endeavors, KB.
     

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