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How to wire the vacuum modulator and tranny kickdown switch questions..

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rocko, Aug 24, 2003.

  1. rocko

    rocko 1/2 ton status

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    Where do I tap in the vacuum line for the turbo 400 on a 5.7 fuel injected engine..

    And how is the tranny kickdown switch wired under the gas pedal? Any schematics would be greatly appreciated...
    Thanks in advance..
     
  2. HarryH3

    HarryH3 1 ton status Author

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    The vacuum modulator needs to see vacuum directly from the intake manifold. Carbed engines had a fitting just behind the carb, with multiple ports available. You may have to get creative on a TBI engine to find a suitable spot. /forums/images/graemlins/frown.gif

    The switch wiring requires switched 12 volts (hot in RUN only), fed through a small fuse (3 amps is what keeps popping up my mind...) to one of the wires. Then the other wire connects to the connector on the tranny. When the switch closes, it applies 12 volts to the downshift solenoid. /forums/images/graemlins/cool.gif
     
  3. rocko

    rocko 1/2 ton status

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    Thanks Harry...
    I'll attempt it.. shouldn't be too hard.. I'll just put a T fitting to a vacuum line off the tbi or manifold.
     
  4. desertrat67

    desertrat67 Hawk Driver

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    The BB and SB manifolds might e different(this is an 88 TBI BB), but this is where mine connects.
    [​IMG]

    And if you have any photos of the kickdown switch could you post those? The one on my truck has never been connected since i have owned it and i would like to hook it up. There is nothing connecting to the tranny nd i have no idea where the switch inside the cab is.
     
  5. Rolled

    Rolled 1/2 ton status

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    The TBI small block is the same as the above pic.


    desertrat67 -

    The kick down is located right on top the gas pedal. If there is a switch attached to the gas pedal, you have one, if not, stop looking for it and go to the junk yard. They are easy to find and should only cost $5. Look in Caddies for a faster find or start looking in 3/4 and 1 tons. easy to pull and easy to install.

    There will be a male connecter,easy to see by bending down, on the drivers side of the th400. That is where the other side of the kick down gets wired to.

    Good luck
     
  6. rocko

    rocko 1/2 ton status

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    I have all the parts needed... just need to get it hooked up..
     

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