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Thread: 6l80 hard downshift 6-2 need solution

  1. #1

    6l80 hard downshift 6-2 need solution

    6-2 downshift on 6l80 is pretty harsh on my yukon

    Tq mgt is stock
    Base tune on 5dpf suggestion
    I change shift timing on 6-2 to have an higher value


    I need suggestion because when i slam it, I can hear a bang in the trans.

  2. #2
    Tuner in Training Mbrowning's Avatar
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    Post a file for us to look at.
    A log would help too.

  3. #3
    Senior Tuner Frost's Avatar
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    Quote Originally Posted by elerico View Post
    6-2 downshift on 6l80 is pretty harsh on my yukon

    Tq mgt is stock
    Base tune on 5dpf suggestion
    I change shift timing on 6-2 to have an higher value


    I need suggestion because when i slam it, I can hear a bang in the trans.
    6-2 is pass-through-neutral. Go to your spark timing tab and check to make sure that tq management advance is still allowed -20deg. If you set that table to zero deg or higher, you are basically causing a WOT neutral-drop during that down shift and it's very harsh (as you've noted).
    Steve Williams
    TunedbyFrost.com


  4. #4
    Spark minimum table is close to zero at wot...

  5. #5
    Tuning Addict 5FDP's Avatar
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    Make it more negative and see if it helps. I keep negative timing in the lower rpm regions all the up to 4,000ish rpm and slowly ramp it down to like -5ish above that.

    I can't say I've done many 6-2 downshifts because I don't allow for 6th gear until over 50mph so if I floor it above that it just shifts into 3rd. I could see that downshift if it was in 6th gear by 40-45mph though.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

  6. #6
    Base tuning 5Fdf following your recommandation was awesome

    This is the only trouble i have when i floor it

    Tq management is still untouch

    Should u disabled neutral downshift ?

  7. #7
    Senior Tuner Frost's Avatar
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    Quote Originally Posted by elerico View Post
    Spark minimum table is close to zero at wot...
    Put that table back to stock and then re-test 6-2 downshift. That table or the one I mentioned will hold spark too high during the pass-through-neutral downshift. Your right foot is on the floor when this downshift is commanded; you MUST allow the ECM to limit torque during this move (through neutral), and this is how it does it. You can have a 500+rwhp car still able to make this downshift, and quickly, but the ECM needs to be able to pull spark. The two tables I have mentioned are very "blunt instruments".

    If it's STILL rough, and it shouldn't be, set all of your downshift times and pressures back to stock and re-test the downshift. This will tell you where to go from there.
    Last edited by Frost; 17 Hours Ago at 10:52 AM.
    Steve Williams
    TunedbyFrost.com