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turbo 400 down shift solonoid

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  • turbo 400 down shift solonoid

    Turbo 400 in a swamp buggy. No need for downshift. When i overhaul the tranny this off season, i plan to do away with the thru housing electrical connection. I f i also remove the solonoid, do i have to block off the hole where the solonoid is connected to the housing or can i leave it open ?

  • #2
    Boy, do i remember that title of FNG !!

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    • #3
      leave the solenoid in place, but don't connect it's wire to anything. then you won't need to worry about it.

      But if you want to eliminate the solenoid, for some reason, look at it, and see what it does. I think it is blocked when not energized, and opens when energized, so that means that you'd want to block the hole. been a while since I looked inside one.

      My fabulous web page

      "If it don't go, chrome it!" --Stroker McGurk

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      • #4
        i hope youre running some sort of full manual valvebody.
        that solenoid also bumps the clutch apply pressure in 2nd
        at WFO, without it the trans will eventually start slipping....

        heres a copy/paste from ( https://www.onallcylinders.com/2014/...like-3-speeds/ )


        When the linkage hits WOT, this completes the circuit to connect the transmission to full system voltage.
        This electrical input powers up a solenoid in the transmission that accomplishes the same results,
        with higher line pressure and a signal to downshift the transmission.

        Often when a TH400 is swapped into a different vehicle, this downshift electrical switch is overlooked.
        Besides the loss of any kind of downshift function, the real danger is that under WOT the transmission
        has not been commanded to increase line pressure. This causes not only a soft upshift, but also damage
        to the clutches because the lower line pressure increases the potential for slippage on upshifts.

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        • #5
          X2 What Fatz said . I put a 400 in a Small blocked S10 and didn't think I needed it . Now , I did generally shift it manually which probably helped but that old farm truck tranny would have lasted longer than 2 years with it connected .
          Previously HoosierL98GTA

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          • #6
            Originally posted by Dan Barlow View Post
            X2 What Fatz said . I put a 400 in a Small blocked S10 and didn't think I needed it . Now , I did generally shift it manually which probably helped but that old farm truck tranny would have lasted longer than 2 years with it connected .
            yep, its an often overlooked thing that has eventual consequences ESPECIALLY with high powered combos.
            shifting manually with a normal valve body at least applies the band as well as the clutches but still doesnt
            jack the line pressure. a full manual valve body will increase apply pressure 100% of the time, although
            extreme pressure increases might cause case failure if you got a microscopic crack or porosity--but ive
            never had that happen myself, only read about it on the internet so you know it must be true, hah hah....

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