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VSS for TPI

Discussion in 'The Garage' started by Hossbaby50, Nov 24, 2003.

  1. Hossbaby50

    Hossbaby50 3/4 ton status

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    I am in need of info on VSS. I need to run VSS for my truck to be emmisions legal in AZ. I am running a 700R4 and from what I read they all have VSS. Is this correct? Can I use the VSS output they have to drive the VSS for the TPI computer? Or do I need an aftermarket VSS box to use? Thanks

    Harley
     
  2. azblazor

    azblazor 1/2 ton status Premium Member

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    I have had to run a seperate aftermarket VSS for both TBI conversions I have done, 4x 700r4 both of them.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    VSS for the '85 truck (actually all our trucks with VSS) and TPI are both the same, 2 pulse.

    Just get the right VSS buffer, there are about three styles. (connectors are different) GM cars from '81 up (GM did change the pulse count in about '94?? though) will likely have the right buffer if yours won't work...output is for cruise and/or ECM only. Your buffer may already be setup for one more "output", you'd just have to find the connector for it if so.

    All 700's use VSS, but it's for the lockup only, at least on the early trucks like yours. You have all the stuff to run the TPI VSS except that wiring connector that runs to the ECM harness from the buffer.

    Initially my TPI will be running off of the stock truck speedometer VSS, later I will go to the electric speedometer to get rid of the "bad" mechanical speedo.
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    All 700's use VSS

    [/ QUOTE ]


    You mean all 700s in EFI applications, right?
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    No, all 700's.
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    So mine had one? If so, where?
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    The "sensor" is bolted to the back of the speedometer. The buffer (usually light blue or yellow) is hanging behind the gauges somewhere.

    Box that controls cruise/converter lockup via VSS (and other input) is above the gas pedal.

    Even if the truck didn't have a 700, and it's the right vintage, almost all speedometers are setup to accept VSS.

    Just flip a speedometer over and look at the small rectangular hole with a tiny (7MM?) bolt hole next to it.
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Ahh so it must still be in the dash and I don't even know it? /forums/images/graemlins/rotfl.gif
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Probably. You'd likely remember trying to get that little tiny screw out...you have to when you remove the gauge cluster. (or unclip it from the buffer, which is usually inaccessible.)
     
  10. Hossbaby50

    Hossbaby50 3/4 ton status

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    So you say it was used to run the cruise control correct? So there should be a VSS wire already in my engine bay that controlled the cruise control. I have the connector that was hooked into my cruise control marked and still hanging in my engine bay. You wouldn't by change know which pin or connector was the VSS output would you? That would make life really easy. Thanks

    Harley
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    Actually the VSS is under the dash. VSS is run off of the back of the speedometer itself. Three wires run from the buffer to the speedometer, but they are a sort of "ribbon" cable, all three stuck together. The wire under the hood would be whatever "output" comes from the cruise box, not the actual VSS output I'm sure.

    Can't tell you what position on the buffer connector is the VSS (although I don't *think* that changed) or what color, as that could change based on year or vehicle. Best idea is to find someone with an electrical manual for your year of truck and get them to tell you. Other option is to find the buffer, and trace the wires from the buffer. If you are lucky, one goes to ground, one to power (fuse panel likely) and one to the cruise box. Some VSS buffers used 3 connectors, some could only take 2, so you really need to find the buffer and trace the wires/look at the connector for your next step.

    If your TPI setup is out of a mechanical speedo F-body, the wire from the I/P connector to the VSS should be the same color all the way to the buffer (maybe match the one in the truck now), although some of them change color from the ECM side of the I/P to the gauge/fuse panel side of the I/P. You'd need to know what pin of the I/P was VSS to know what color wire the F-body used that year to the VSS.
     

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