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VSS/Speedo/torque converter lockup??

Discussion in 'The Garage' started by MTBLAZER89, Aug 12, 2003.

  1. MTBLAZER89

    MTBLAZER89 3/4 ton status GMOTM Winner

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    Ok I know these things work together right?? Anyway after my gear swap my speedo now reads "faster" than I am really going. Driving about 25 in D (speedo reads "about" 35) the torque converter is locked up causing the engine to idle along at about 1100. Problem is just enough throttle to maintain that speed I get sort of a vibration cause it's lugging the motor. Also happens in OD around 65. Will changing the speedo gears change when the torque converter locks up??
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Yes.

    VSS controls the "low speed" threshold of the TCC lockup, and VSS is run off the speedo gears (essentially), so if the speedo cable is turning fast enough that it indicates 35MPH, TCC will be commanded to lock. (assuming all other conditions for lock are met)

    So...since your speedometer says 35MPH, and that is likely the lockup MPH, the TCC is locking when it should be, based on it's input.
     
  3. MTBLAZER89

    MTBLAZER89 3/4 ton status GMOTM Winner

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    anybody else care to elaborate?? /forums/images/graemlins/ears.gif
     
  4. Fletch79

    Fletch79 Registered Member

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    Fix your speedo and it should clear up.
    I believe your VSS is your spedometer, and that the ECM takes it's reading right from the dash.

    You could put in a switch to control the lockup manually, but why?

    You could also pull the EPROM out of your ECM, Read the binary image into a PC, alter the settings to accomodate your inaccurate speedo, burn a new chip with the new settings, install it in the ECM, and feel silly for not fixing the speedo.

    Sounds like you know what you need to do, but you asked for an elaboration.

    /forums/images/graemlins/thumb.gif
     
  5. MTBLAZER89

    MTBLAZER89 3/4 ton status GMOTM Winner

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    Yep just gettin some ideas I am gonna change the speedo gears anyway, but I was just wondering if it was related to my "engine bogging/vibration problem" under lockup at low RPM's. Right now I just use 2 in town and D on the hi-way never even notice it then cause the revs are higher /forums/images/graemlins/thumb.gifeven though I still don't know how fast I'm going. /forums/images/graemlins/eek.gif
     
  6. Fletch79

    Fletch79 Registered Member

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    If your problem goes away when you force the motor into higher revs, then it sounds like you have the loading diagnosed correctly.

    Let us know how it turns out.

    /forums/images/graemlins/thumb.gif
     
  7. MTBLAZER89

    MTBLAZER89 3/4 ton status GMOTM Winner

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    Gears are dealer items right??
     

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