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Thread: 8.1/Allison 6spd TPS values/adjusting

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    Default 8.1/Allison 6spd TPS values/adjusting

    I am using an A40 TCM from a 2006, Chevy 8.1L, with an Allison 6-speed. When viewing the tune file, the shift parameters are TPS/MPH, or TPS/RPM, etc. It is my understanding that the 8.1L TCM does NOT 'see' TPS, but rather it gets calculated torque from the 8.1 ECM. My problem is: If the value being sent to the TCM is engine torque, how can a person make intelligent adjustments to shift points that are TPS/x based? Shouldn't it be Engine Torque/RPM, or Engine Torque/MPH? I have no way of knowing what, for example, 75% TPS equates to in engine torque.

    I searched the forum for several hours looking for info on this, but came up with nothing related.

    Anyone have any experience with this setup?

  2. #2
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    I'm pretty sure the ALLISON TCM does all of it's shifting via a throttle value, and defuels based off of a torque value. Sounds like your using a stand alone setup which means it is defaulting back to an analog TPS signal so it will be using TPS VS MPH for shifts.
    1995 GMC 2500 SUBURBAN powered by 01 DURAMAX/ALLISON, little of this, a little of that,
    DIAMONDEYE 4" exhaust, CORSA muffler, AFE stage 1 dry filter, custom tuning by me, KENNEDY single pump and pump rub kit.

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    None of the TPS PIDs register TPS. I am not using an analog TPS, however. The TPS I am using is a PWM type. The more 'throttle' you give it, the more engine torque is displayed. I can watch the values on SCAN, using Engine Torque PID.... But nothing shows up on TPS. Which isn't really my main concern, since the 8.1L TCM does NOT have TPS input. It gets torque values from the ECM. Which I can duplicate. My issue is simply knowing what amount of given torque equals what % of TPS. Since the 8.1L TCM uses engine torque, rather than TPS, it would be nice to see the tables listed in Engine Torque/MPH or /RPM.

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    I have the same setup for a stand alone when we have it hooked to EFI laptop mine is showing tps percentages.I have over 1000 miles on it have to do some fine tuning with lockup and mph 4,5,6,I have them shifting to low.tapshift work good and have lockup 2nd though 6th in drive.haven't had time to see why TH don't work I think I forgot one wire to my notes that is what I get for getting in a hurry.

    Dale

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