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Thread: 98 K1500 Speedo Help

  1. #1
    Tuner in Training
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    98 K1500 Speedo Help

    I am trying to use the tire gear wizard on my 98 k1500. The tire size is 32.8 and the gears are 4.11's. When I confirm this change it maxes out my transmission shift tables to 256mph and causes the truck not to stay in first.

    What am I doing wrong? I would try to manually change the VSSppm but I am pretty new at this and don't want to hurt anything.

    This truck is not 411 swapped. Tune is attached

    Thank you.

  2. #2
    Tuning Addict 5FDP's Avatar
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    What is the stock value in that tune for the tire size?
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
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    Quote Originally Posted by 5FDP View Post
    What is the stock value in that tune for the tire size?
    Stock value is 0.86. I think I know what Is wrong. For whatever reason the stock tune has a 1.0 for the reluctor teeth. If I change that value to 40 teeth and go back into the wizard the stock tire size value is 30 which would make sense. So I?m going to change the tire size to 32.8 and change my gears to 4.11 and see what happens.

  4. #4
    Advanced Tuner Shrek's Avatar
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    Quote Originally Posted by codemain19 View Post
    ... For whatever reason the stock tune has a 1.0 for the reluctor teeth ...

    I have not tuned one of these old Vortec PCMs in a long time, but I recall believing that some of the Speedometer parameters were incorrectly labelled.

    A 1998 4L60 will likely have "1" in the reluctor teeth box, while a 1998 4L80 will likely have "31" in this same box. I recall believing that this was actually the number of teeth on the ISS (a 4L60 does not have an ISS, hence a value of 1).

    I always used a different tuning software package for these PCMs, any time that I needed to correct the Vehicle Speed / Speedometer output.

  5. #5
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    Quote Originally Posted by Shrek View Post

    I always used a different tuning software package for these PCMs, any time that I needed to correct the Vehicle Speed / Speedometer output.
    What different tuning software did you use?

  6. #6
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    Quote Originally Posted by codemain19 View Post
    What different tuning software did you use?
    I use Tunercat OBD2 on those.