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Thread: Pentastar Challenger not shifting at WOT

  1. #1
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    Pentastar Challenger not shifting at WOT

    Hey guys, I can't seem to find anyone with a similar problem.

    After upping the shift points to what I think is around 6700rpm for each gear at WOT, the car won't shift gears at full throttle. It just stays up at redline. Is there anything in the tune that I'm not seeing?

    I figured the Engine/Fuel/Cutoff might be doing it, but I raised that over 6700rpm and it still has the issue. You can see an example in the log at 11 minutes in.

    v18withTrans.hpt
    1-5-20-2.hpl
    2002 Silverado extended cab 5.3L.
    Volant cold air intake
    Gibson cat-back exhaust
    Electric fan conversion


    2016 Dodge Challenger SXT 3.6L
    Hellcat airbox
    Ported throttlebody
    Pedal Commander

  2. #2
    Hi,
    I take a look at your tune. The TCM rpm limit is set at 7200 rpm, and it's upper than your engine rev limit (7000 rpm at maximum, other are 6800 OR 6900 rpm). Your shift patterns are also strange, max rpm I saw is 7745rpm... If you want the car shift again at wot, I think that you should set tcm rpm limit at 6800 rpm and max upshift in shift pattern table at 6800 rpm to.
    I never tune ZF8 but NAG1 tuning works like that.
    What tables have you modify before your issue?

    P.S. : sorry if my English is bad, I'm french, and still Learning your language...lol
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    Last edited by arbracam26; 01-14-2020 at 02:25 AM.

  3. #3
    Senior Tuner mbray01's Avatar
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    If your shift rpm is too close to your rev limiter, it will not shift, you need to give it time to shift.
    Michael Bray
    Rusty Knuckle Garage
    Slidell, Louisiana
    20yr Master Tech.
    Advanced Level Specialist
    Custom Car Fabrication, Customization, High Performance.
    GM World Class Technician
    Shop Owner

  4. #4
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    Thanks for looking at it guys! And your English seems to very good.

    I dropped the RPMs down a little from what I thought was 6800 rpm to around 6700 rpm for each shift. But you're saying that my shift patterns are up at 7745? Did I do my math wrong? I thought it was a simple multiplication by the gear ratio of the current gear.
    zf8 1= 4.71
    2 = 3.14
    3= 2.10
    4 = 1.67
    5 = 1.29
    6 = 1.0
    7 = 0.84
    8 = 0.67

    So for first gear, 1443 rpm x 4.71 = 6800 rpm shift point. Is that right?

    I figured a few hundred rpm would be a sufficient gap between limits, but maybe I need more?
    2002 Silverado extended cab 5.3L.
    Volant cold air intake
    Gibson cat-back exhaust
    Electric fan conversion


    2016 Dodge Challenger SXT 3.6L
    Hellcat airbox
    Ported throttlebody
    Pedal Commander

  5. #5
    Advanced Tuner
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    Feb 2016
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    431
    Quote Originally Posted by Hoho View Post

    So for first gear, 1443 rpm x 4.71 = 6800 rpm shift point. Is that right?

    I figured a few hundred rpm would be a sufficient gap between limits, but maybe I need more?

    You will need more gap than that in the lower gears.
    There are delays (in ms) in the shift software that sequence the clutches.
    You can mess with those but it is tricky...its way easier just to command the shift a little earlier.

  6. #6
    Tuner
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    Ah ok, makes sense!

    Thanks for the help everyone.
    2002 Silverado extended cab 5.3L.
    Volant cold air intake
    Gibson cat-back exhaust
    Electric fan conversion


    2016 Dodge Challenger SXT 3.6L
    Hellcat airbox
    Ported throttlebody
    Pedal Commander