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Thread: 6 Spd upshift torque reduction

  1. #41
    Lifetime Member LB72004's Avatar
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    Wheelz,

    are you saying that with less then 200 ft-lbs of commanded torque you dont have any defuel? i have contemplated doing the same thing on mine thinking that it should be fine with low throttle/torque for better shift feel.
    2008 Chevrolet 3500HD DRW LTZ
    285/75/17 Nitto Dura Grapplers, 4.56 gears, Front and rear ARB lockers, Efi Live tuning by me, Raptor 160 LP, Cognito 4-6 NTB Lift, 4" Exhaust, Built Trans by Mike L.

    Sold - 2004 LB7 Duramax, EFI Live with DSP5 Tune
    stage 4 SC transmission, 265/70/16 tires

  2. #42
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    Yep. In my head it makes sense that you defuel to protect from excessive torque and to accelerate the shift. Under low power the tranny will shift fine without defueling. But you still de-fuel under high load to protect it during high power shifts.
    14 GMC Sierra
    5.3L CC SB 4x4
    Basic tuning....

  3. #43
    Lifetime Member LB72004's Avatar
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    thanks, i will give this a shot and see how it feels
    2008 Chevrolet 3500HD DRW LTZ
    285/75/17 Nitto Dura Grapplers, 4.56 gears, Front and rear ARB lockers, Efi Live tuning by me, Raptor 160 LP, Cognito 4-6 NTB Lift, 4" Exhaust, Built Trans by Mike L.

    Sold - 2004 LB7 Duramax, EFI Live with DSP5 Tune
    stage 4 SC transmission, 265/70/16 tires

  4. #44
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    I make no promises, but you may have to experiment with the value to defuel to.
    14 GMC Sierra
    5.3L CC SB 4x4
    Basic tuning....

  5. #45
    Lifetime Member LB72004's Avatar
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    after looking over my LB7 tune, this looks to be a lot harder then i originally thought. seems that the tunes are not set up to be able to do this. looks like i would have to do a lot of logging and tweaking till i got a mm3 number that matched the throttle based injection quantity while also shifting/defueling

    right now the mm3s in the torque limited injection quantity equals the throttle base in injection quantity and it still defuels. i believe the transmission requests a defuel percent and the ECM looks at the torque limited injection quantity table and subtracts the percent from it. the problem is not knowing what percent the transmission will ask for.

    seems like this would be easier i the later years but not the LB7 and LLY

    any thoughts?
    2008 Chevrolet 3500HD DRW LTZ
    285/75/17 Nitto Dura Grapplers, 4.56 gears, Front and rear ARB lockers, Efi Live tuning by me, Raptor 160 LP, Cognito 4-6 NTB Lift, 4" Exhaust, Built Trans by Mike L.

    Sold - 2004 LB7 Duramax, EFI Live with DSP5 Tune
    stage 4 SC transmission, 265/70/16 tires

  6. #46
    Lifetime Member GMC-2002-Dmax's Avatar
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    Shift quality is the hardest thing to dial in on the earlier years, it takes a long time to get it perfect at all TPS%/RPMS.

    You are correct, its not easy
    www.mscservices.net


    Tuner of many, many Duramax and Cummins Diesels.


  7. #47
    Lifetime Member LB72004's Avatar
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    true, true..

    my shift quality is not bad by any means, it is actually quite good. i currently use a excel spreadsheet to dial it in and it seams to work the first time. i have not run yet with any defuel so i was wondering if it would be any better and the low torque areas would be the way to test it, but it is not that easy
    2008 Chevrolet 3500HD DRW LTZ
    285/75/17 Nitto Dura Grapplers, 4.56 gears, Front and rear ARB lockers, Efi Live tuning by me, Raptor 160 LP, Cognito 4-6 NTB Lift, 4" Exhaust, Built Trans by Mike L.

    Sold - 2004 LB7 Duramax, EFI Live with DSP5 Tune
    stage 4 SC transmission, 265/70/16 tires

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