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TH400 tranny question

Discussion in 'The Hokey Ass Message Board' started by Truckedup, Apr 27, 2013.

  1. Truckedup
    Joined: Jul 25, 2006
    Posts: 4,214

    Truckedup
    Member

    I'm working on 64 Chevy truck that had a TH 400 tranny swapped in.The tranny was pulled and it's disappeared. I now have a TH 400 from and 80's motor home.
    The tranny has an electric switch by the linkage with an external wire connection. I assume this is the kick down switch? And it has a vacuum modulator.
    I need to get this thing running and out of my garage. If I just hook up the modulator and not the kickdown switch will the tranny function good enough to drive? By drive I mean it will shift up through the gears...manual downshifting is ok.
    Thanks
     
  2. You'll need manifold vacuum to the modulator.
    It should drive&shift normally if everything else is in order.

    & the switch for kickdown is triggered off of the throttle.

    By the linkage switch might be for Motörhome back up lights or neutral safety switch so be careful
     
  3. You can run a T400 without the electric kickdown hooked up. I have done it in several cars. The kickdown switch, when you decide to install, mounts to the carb linkage, some mounted right at the gas pedal.
     
  4. Truckedup
    Joined: Jul 25, 2006
    Posts: 4,214

    Truckedup
    Member

    Thanks guys.....What actually makes the tranny to drop down a gear ? I see no mechanical connection between the "switch" and the tranny itself.
     

  5. The connector on the side of the transmission is hooked to the solenoid which "kicks" it down electrically inside the transmission. This solenoid is wired to the kickdown switch at the carb or throttle pedal
     
  6. chubbie
    Joined: Jan 14, 2009
    Posts: 2,318

    chubbie
    Member

    It's a elect. kick down. does it have 2 wires or one? Some of those motor homes had a switch pitch torque converter
     
  7. Truckedup
    Joined: Jul 25, 2006
    Posts: 4,214

    Truckedup
    Member

    I'm not home right now but I believe it had more than two wires.
     
  8. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    56sedandelivery
    Member Emeritus

    Like everyone else has already said, if it's a single terminal "kickdown" you'll be fine without it. You can manually pull down into a lower gear, but unless it has a shift kit/modification, first gear won't pull down until your speed slows down enough. With a shift kit, any speed, and you can drop down in gearing. If the trans came from a motor home (a larger one), it probably has "HD" cast into the bell housing; the case is thicker in some areas and the planetaries are straight cut gears in those transmissions. They are stronger, but noisier because of the straight cut gears. Very doubtful you have a switch pitch TH400, but there would be two terminals if you did. Butch/56sedandelivery.
     
  9. Truckedup
    Joined: Jul 25, 2006
    Posts: 4,214

    Truckedup
    Member

    Yes,HD on the bellhousing . I think it has more than one wire,I check later when I'm home
     
  10. Are you looking at a switch ?
    Or are you looking at a plug ?


    There's a solenoid inside the transmission, (plug on the outside) when 12 volts is applied to this solenoid it provides the kickdown and extra line pressure.
    The actual switch for the solenoid is actuated by the throttle when it's nearly WOT. Some are a little slider right under the gas pedal arm ( Chevy truck , Chevelle , some are plunger style on the carb, some are rotary on the carb, aftermarket are plenty .
     
  11. Truckedup
    Joined: Jul 25, 2006
    Posts: 4,214

    Truckedup
    Member

    On the left side close to the shifter arm was a small device with what I thought was a multli wire plastic connector wire(s) I was a quick look because I had to be somewhere, but my first thought was a switch.......
    I have come to a gun fight armed with a knife ...Will return with better info....
     
  12. Lukcarnut
    Joined: Apr 6, 2013
    Posts: 41

    Lukcarnut
    Member
    from California

    Its a single male spade connection that gets a positive when you push down to full throttle, either through a pedal mounted switch or one off the carb or throttle body. It will work fine without it being hooked up. You will just have no kickdown, you can downshift manually. I would eventually hook it up though because you can put extra strain on the trans if you have lots of power and forget the down shift or dont do it at the right times.
     
  13. 574door
    Joined: Apr 25, 2013
    Posts: 9

    574door
    Member

    lukcarnut is spot on... TH400 should have a single spade terminal on the driver side that requires 12V to kick down. I discovered mine was never hooked up when I was replacing my driver side floorboard. I had driven my car for one driving season before tearing into it with only the vacuum on the passenger side. It helps you up shift while daily driving... like others have said, when you floor it and don't kick down, your not getting the proper performance, that's all. So to hook up the electric kick down you could use

    http://www.summitracing.com/parts/bmm-20297?seid=srese1&gclid=CMG7kumV7LYCFaV_QgodrlwA_A

    I'm going a little less conventional and using a simple switch

    http://www.colehersee.com/home/item/cat/257/8486-05/

    You can find them for about $10

    Good Luck!
     
  14. Truckedup
    Joined: Jul 25, 2006
    Posts: 4,214

    Truckedup
    Member

    I looked at the TH400 closely.....Yup,one wire terminal on the left side.The multiwire harness is a switch on the tranny shift lever that now serves no purpose
     

  15. Switch is probably a motor home specific leftover but that's just a guess. Maybe check it out with a volt meter and see what it does???

    Single wire terminal is where your +12 volts for kick down goes.

    You can manually down shift yes, but there's still a night and day difference with the solenoid hooked up. A manual down shift is like a nice shove, with the lockdown it's like good swift kick in the ass.
     

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