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T400 Tranny folks, downshifting questions

Discussion in 'The Garage' started by bobsurf, Apr 14, 2003.

  1. bobsurf

    bobsurf 1/2 ton status

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    I'm trying to figure out my buddy's problem he's having with his '86 2wd 3/4 ton. He's got a T400 in there, and I know very little about them (I've got a TH350). He's having problems with it not wanting to downshift when he either kicks it down, or just regular driving (from what he told me).

    What I've read so far:

    There is a kickdown switch hooked up to the skinny pedal. I'll check to make sure that's working (i.e. ignition on, hook it up to a light, floor it).

    From what I read, there isn't a TV/Detent cable, but instead is just controlled by the vaccum modulator. Where is that? Is that what we should check next? Is there anything else that plays a role with auto shifting?

    Thanks in advance.
     
  2. Swanson52

    Swanson52 1/2 ton status

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    There should be a vacuum line from the back of the manifold to the passenger side of the trans, where there is a modulator. The switch for the kickdown is on the driver's side. The vacuum line specifically controls the upshifts. Not much help...sorry. /forums/images/graemlins/crazy.gif
     
  3. Don

    Don 1/2 ton status

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    The kickdown is an electric operated solenoid, located on the valve body in the trans.

    Pull the pan, make sure You have a signal when the pedal is pushed to the floor, or You might get lucky, and the connector has simply fallen off of the solenoid. /forums/images/graemlins/grin.gif
     
  4. Klink K5

    Klink K5 1/2 ton status

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    Check to see if the oarnge wire had fallen off the trans on the drivers side. I've seen this happen alot on the TH400 trannys. /forums/images/graemlins/thumb.gif
     
  5. bobsurf

    bobsurf 1/2 ton status

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    Thanks Everyone, I'll do some more investigating.
     

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