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Thread: 4t45e cant get it to shift @ 7000rpm

  1. #1

    4t45e cant get it to shift @ 7000rpm

    Having some issues raising the rev limit on my 4t45e to 7000rpm from 6500. When it tries to shift into the next gear at WOT it just hangs up and wont shift. I used a calculator for gear ratio and tire size to determine the appropriate shift mph difference and came up with 3mpg on the 1-2 shift 6 mph on the 2-3 shift and 8mph on the 3-4 shift but it still hangs up. Does anyone have any insight into this?

  2. #2
    Senior Tuner cobaltssoverbooster's Avatar
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    Please move to transmission..Thank you.

  3. #3
    Advanced Tuner CatnipG5Bandit's Avatar
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    Also post a tune. What are your other engine limiters set to?
    2008 Pontiac G5 2.2L (main oil seal became a crunchy Autumn leaf, RIP)
    2016 Fiesta 1.0L Ecoboost - Project "not-so-detestable"

  4. #4
    Advanced Tuner
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    MPH is probably too high though you didn't specify which gear is not shifting. If it's the 1>2, then lower it by 3 mph and see if it shifts. If you have problems with all of them, lower each one by a couple mph and see if it shifts.

  5. #5
    Quote Originally Posted by JimmyS View Post
    MPH is probably too high though you didn't specify which gear is not shifting. If it's the 1>2, then lower it by 3 mph and see if it shifts. If you have problems with all of them, lower each one by a couple mph and see if it shifts.
    Sorry forgot i posted in the wrong forum. So the only condition where the trans will not shift due to this change is if the mph is set to high? Ill cut my changes by half and see how it responds.

  6. #6
    Advanced Tuner
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    It might not be the only condition but it has happened to me when I started tuning my trans. It is best to check your logs to see when the trans is actually shifting and compare them to the TCM parameters.

    The TCM looks for MPH and RPM to make the shift so both conditions in the TCM have to be met before it will shift. Set the MPH a bit lower so that the RPM is the second trigger and you should be fine.

    If my log shows that I'm actually shifting at 36mph and 7000rpm, my mph setting at WOT is most likely set at 32 +/- 1. That's just an example. You don't want to get the mph and rpm too far apart though because it can also cause shifting problems. Try to keep the mph 3 to 5 mph lower than the log shows where it shifts at and then adjust the rpm up. Run another log and see what mph it shifted at and then adjust your mph accordingly. Repeat until you reach your goal.

    There's a good read on transmission tuning with HP Tuners on the LS1 GTO site. I can post the link if you haven't read it.