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Tranny won't upshift ... vacuum? other?

Discussion in 'The Garage' started by dremu, Dec 11, 2006.

  1. dremu

    dremu Officious Thread Derailer Premium Member

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    Summary: Just had the TH400 rebuilt in my CUCV, and also had some fuel leakage issues. I R&R'd the tranny and took it bare to the shop.

    Tranny is back in now and shifts into reverse and drive okay, but runs in first gear regardless of D-2-1. :(

    I would swear the vacuum line is connected properly, but she winds up something fierce and never goes out of first.

    If the vacuum is not getting to the modulator, would that cause this behavior? Said another way, what's the mechanism by which the tranny upshifts from 1 to 2 to D?

    -- A
     
  2. destinbeachman

    destinbeachman 1/2 ton status

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    Stuck governor or zero vacuum at the modulator.
     
  3. dremu

    dremu Officious Thread Derailer Premium Member

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    Whassa governor? Internal part?

    -- A
     
  4. HarryH3

    HarryH3 1 ton status Author

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    Turbo 400's use an electric kickdown solenoid to force downshifts when you romp the loud pedal. Make sure that the kickdown switch isn't messed up. When there is 12 volts applied to the electrical connection on the side of the trans it will try to stay in low gear as long as possible. You can unplug the connector right at the trans and take a test drive to see if it makes any difference.
     
  5. dremu

    dremu Officious Thread Derailer Premium Member

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    Ah yes. I know about the electric kickdown, but forgot to think it might be kicking all the time.

    Thanks all!

    -- A
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    As an addition, I can't recall even what the piece was, but there is a valve in there that you sometimes gets "stuck" (in my case after a rebuild) and running it manually through all forward gears eventually unstuck it, and never did it again. I have a feeling it was the governor, unsure how running it manually through the gears helped, but it did. Probably varying fluid pressure.

    Run through all the other suggestions first, then maybe try the above at varying engine speeds.

    FWIW my TH400 would shift fine without vacuum to the modulator, the only difference seemed to be how hard it shifted. From playing with an adjustable modulator, the shift speed changed at most 5MPH from modulator adjustment.
     
  7. dremu

    dremu Officious Thread Derailer Premium Member

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    Heh. Well, some red-headed idiot (i.e. me :whistle:) had to loosen the vacuum pump to get the intake manifold off to do the fuel lines, so it's possible that the vacuum got borked up then.

    Or maybe I need to shake that governor thing loose. Grrr.

    -- A
     
  8. dremu

    dremu Officious Thread Derailer Premium Member

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    Followup: Vacuum. Vacuum. Vacuum.

    Vacuum: It sucks. :haha:

    Replaced some lines that were dry & cracking and fiddled with the regulator-valve thing on the throttle, and she's all better now. The guy who rebuilt the tranny is gonna tweak the modulator setting for me, and all is well.

    Thanks all!

    -- A
     

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