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Thread: Trans Turbine RPM Spike, RPM Limit

  1. #1
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    Trans Turbine RPM Spike, RPM Limit

    I trying to figure out what to change in my TCM tune to eliminate a Trans Turbine RPM spike on my shifts that causes me to tap the rev limiter, close the throttle and cut fuel. You can see the engine rpms stay in check through the shift, but as soon as it appears the trans is completing the shift, the trans turbine rpms sky rocket to 7,000+ rpms. Thoughts?

    This is a Paramount Super Pro trans, 2800 stall, Ding's Valve Body, behind a 4.5L Whipple setup with a 426ci motor (around 900whp currently).

    Whipple Tune6 3-4 Shift.hpl

  2. #2
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    It sounds like you are describing shift flare.

  3. #3
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    Yes. But not showing in the engine RPM, only in trans RPM

  4. #4
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    Is one pid (RPM) polling at a faster rate?

    That doesn't make sense to me otherwise.

  5. #5
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    Quote Originally Posted by spoolboy View Post
    Is one pid (RPM) polling at a faster rate?

    That doesn't make sense to me otherwise.
    Ah ha, you are correct! clearly can see its slower polling.

    But regardless, back to the original question, shift is commanded at 6500 rpms, I can see it commanding a shift starting right around 6500, but flares to 6900-7000rpms before it completes the shift. Any suggestions on fixes to get it to shift earlier before the rev limit?

  6. #6
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    No I don't think I know how to fix it. It's possible that something is hurt in the trans and it can't "grab" the next gear as quickly as it should. Clutch or band or something in the system that applies them.

    Does it do it on every gear change, or just a specific up-shift? Does it get worse in higher gears or at higher road speeds?

    I'm trying to figure out the 8spd transmissions right now and also about to yank out and go through the 727 in my wife's Trailduster. Haven't looked at NAG1s.

  7. #7
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    Issue I have with it being mechanical is it acts the same at half the horsepower. Doesn't seem power related, i.e. mechanically related to the clutches slipping. Guessing has something to do with the handoff and pressure applied as the outgoing clutch pack releases, maybe its releasing before its supposed to.

  8. #8
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    Did you recently change the valve body?

  9. #9
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    No, been running a Ding's VB since trans was new. That said I do have the original Paramount valve body I could switch in, just the drivability is pretty horrid outside of WOT. Like getting hit with a sledge hammer every shift.