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Electric Speedo Calibration(Search Done) Need More INFO!

Discussion in 'The Garage' started by Batmanjr, Sep 18, 2002.

  1. Batmanjr

    Batmanjr 1/2 ton status

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    Location:
    Copperas Cove, Texas
    I've done the search on how to adjust the electric speedo, but all that was mentioned was a calibrator. So I found the one made by "Superlift" and the one called "Little Yellow Box", but they all want $100 to $200 for it! I only need to adjust this ONCE! I'm changing the gear ratio in my Father's `94 3/4 ton VAN and want to correct his Speedo so the Vss doesn't crew up the tranny and ECM!
    Are there any other option out there!???? CHEAPER &/or EASIER!

    Thanks in advance!
     
  2. HarryH3

    HarryH3 1 ton status Author

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    Give the local GM dealer a call and ask the parts dept. if there is a speedo calibration kit available for that year. If so, then it isn't too tough to calibrate using the instructions provided with the kit.

    The VSS is a tiny electrical generator that creates a sine wave output. The VSS buffer converts the sine wave into a square wave that is a valid input for the ECM. It is also calibrated to the gear ratio and tire size that the truck left the factory with. Using digital circuitry, it alters the number of output pulses per mile to match those parameters. (So it may be "seeing" 2,200 pulses per mile on the input side, but then only sending 2,000 pulses per mile to the ECM). By altering how the VSS Buffer modifies the signal to the output side, you can change it to match the setup that's right for your gears and tires.

    The cool thing about the VSS Buffer from Superlift is that you can calibrate it for 2 different settings. So if you have one set of tires for the street and a different set for playing in the mud, then you can calibrate it for each set of tires. Then when you swap tires you just flip a switch under the dash to change back to the correct calibration. /forums/images/icons/cool.gif
     
  3. Batmanjr

    Batmanjr 1/2 ton status

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    Grat Info, i will check with the dealer, but does anyone else know how I could calibrate this myself without buying a KIt from the Dealer! I really don't want to be putting too much money into a "VAN"!!! Thanks
     
  4. HarryH3

    HarryH3 1 ton status Author

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    Ya gotta buy the kit, if it's available. It contains an electronic part that you have to clip certain legs off of, based on the ratio that you come up with when you do the math for the gears vs. tire size using the info provided in the kit. /forums/images/icons/mad.gif Then you plug it into the VSS (if yours is even programmable, not all are) and you're good to go.
     

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