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Thread: 1998 f body auto to 6 speed conversion speedo issues.

  1. #1
    Tuner in Training
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    Jun 2011
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    1998 f body auto to 6 speed conversion speedo issues.

    The car was originally a six speed and they changed to auto, when they did they changed the harness and pcm to an auto as well.... Car has been changed back to a six speed but the auto harness and pcm remain, the speedo reads like 15mph at 80 and no matter what I try it doesnt change. HELP!!!

  2. #2
    Advanced Tuner
    Join Date
    Apr 2009
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    If you have stock tire size and 3.42 gear then put in what is in the pic. If you have non stock tire size and diff gear then tire diameter divided by gear ratio is what you need to put in the gear/tire calc page and it will calculate the mile and trans mile.
    1997 Trans Am WS6 - LS1 swap - TR224 - Pacesetter Longtubes - Yank SS3600
    - 3.42 Moser 12 bolt - Wilwood Brakes - HP Tuners tuned - P1SC-1 Procharger

  3. #3
    Tuner in Training
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    That doesnt change anything.

  4. #4
    HP Tuners Support
    (foff667)
    Bill@HPTuners's Avatar
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    Might consider flashing in a manual operating system as there are likely thousands of differences between an auto & manual trans operating system. ESPECIALLY with the 98's since the are a single segment file its ALWAYS best to have the pcm flashed with a manual trans file in a manual trans application.
    It doesn't have to be perfect, it just needs to be done in two weeks...

    A wise man once said "google it"

  5. #5
    Tuner in Training
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    Thank you, That's what I needed... Now if it only didn't cost another 100$ to do it