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tcc clutch

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by marine_enlisted, Oct 20, 2002.

  1. marine_enlisted

    marine_enlisted 1/2 ton status

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    Gents,
    I have an 86 gmc shortbutt 4x4 . Can someone tell me what controls the tcc clutch on my 700r4? I have heard some say there is a vacuum switch and others say there is a small module somewhere under the dash. I'd like to know where these componants are and what they look like. Thanks a lot. Mike /forums/images/graemlins/1zhelp.gif
     
  2. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Well Both my trucks are pre 700R4. Might hit a local Libray in town and see if they have the factory years spicific manuals on MicroFisch. Stuff like Chiltons and Haynes are general but there are some things like wiring harness, emissions stuff, vac lines that is year spiciffic and would be available in those manuals. Usualy 10cents a page for copies.
    Welcome to CK5
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Hmm. Whats your carb look like? Any wires going to it besides the choke?

    Heres what CAN and did in some years, control TCC on GM vehicles, trucks inclusive.

    Module underneath the dash (above the gas pedal) This also controls the cruise control like your year will have, if equipped.

    VSS. Vehicle Speed Sensor bolts to the back of the speedometer head (back of the gauge) and has 3 wires. The buffer is between the "optical eye" at the speedo, and the control module. Its usually light blue, light green, or yellow. Electric cruise uses this input too. Too low speed, and it won't allow the TCC to lock.

    TPS. Throttle Position Sensor was only on CCC carbs (two electrical plugs) and was used in conjunction with the computer controlled distributor. Not real common on the trucks, to say the least.

    Vacuum switch. Locks/unlocks the converter based on engine vacuum. This was used instead of the TPS if not equipped thusly AFAIK.

    The brake switch is to unlock the converter.
     
  4. marine_enlisted

    marine_enlisted 1/2 ton status

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    Carb is long gone with the 305 I'm in the middle of swapping in a 98 350 vortec. I had this same question on chevy talk .com I got a link to an article about it. 86 trucks used a pressure switch in the valve body and a low vacuum switch mounted to the firewall behind the booster and also a brake cut off switch on the pedal Looks like all I should have to do is hook up manifold vacuum to the low vac switch and I should be golden. Thanks for the reply Dorian.

    Mike
     

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