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Thread: TCM shift points

  1. #1
    Senior Member lakingslayer's Avatar
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    Default TCM shift points

    What gives? I've tried raising the part throttle shift speeds and some seem to work some of the time but the TCM seems to still have control and do what it wants to. I'm trying to make it so when I press the throttle past 50% the shift points also go up as the throttle is pressed further. Setting the TCC lockup rpm seems to work but I cannot get it to lock in 2nd gear after 50% throttle. Is there something missing in the TCM tables?

  2. #2
    Forum tyhee Site Admin GMPX's Avatar
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    Default

    In stock form do the speeds indicated in the tables match to what you see?

    Cheers,
    Ross
    Need official EFILive help, please go here.
    For tuning support please post your questions on this forum (or other auto forums).
    Sorry if I don't respond to your PM, don't take it personal.


  3. #3
    Senior Member lakingslayer's Avatar
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    Stock:

    The D5000 table at 0% to 43.8% throttle is set to 16mph and the truck shifts at 14mph when the throttle is at 33%.

    The D5001 table at 0% to 37.5% throttle is set to 29mph and the truck shifts at 23-24mph when the throttle is at 25% .

    The D5002 table at 0% to 37.5% throttle is set to 39mph and the truck shifts at 28 to 29mph when the throttle is at 26% .

    The D5003 table at 0% to 37.5% throttle is set to 55mph and the truck shifts at 37mph when the throttle is at 23%

    Modified:
    The D5000 table at 0% to 50% is spread from 16-18mph and the truck shifts at 14mph when the throttle is at 19%.

    The D5001 table at 0% to 50% is spread from 32-40mph and the truck shifts at 29mph when the throttle is at 25%.

    The D5002 table at 0% to 43.8% is spread from 44-49mph and the truck shifts at 37mph when the throttle is at 22.7%.

    The D5003 table at 0% to 43.8% is spread from 59-69mph and the truck shifts at 48mph when the throttle is at 26.7%.

    These are just one set of data points for the stock and modified trans tables. One of the issues is getting consistent shifts. The speeds can vary 5 to 10mph with the stock file and I don't know why that is. My main question is what does the TCM/ECM use for the Vehicle speeds? It almost seems like the TCM speeds are derived not taking into account the TCC slippage or something.

  4. #4
    Senior Member lakingslayer's Avatar
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    I tried running with T/H on this morning. I have not changed any of the T/H shift points from what the file originally was stock. BTW I'm running an '01 TCM with high idle enabled downloaded form the DP.

    D5000 table is set to 21mph from 0% to 56.3% throttle and the truck shifted at 18mph at 21.6% throttle.

    D5001 table is set to 44mph from 0% to 56.3% throttle and the truck shifted at 33mph at 15.3% throttle.

    That's all the T/H data I was able to get this morning since I forgot to take the scan tool off of pause after I left the fuel station

    I know I am able to make the shift points go up but it would be nice to know how the TCM determines them. Also my Speedo is off my about 2mph (it reads faster) than the EFILive SAE.VSS PID as well as the RPM's reading is lower on EFILive than on the truck dash. To determine the shift points from my log files I'm using the SAE.VSS PID for vehicle speed and using the GM.DMAX_TRQ_DMA PID to get the shift points.

    I really appreciate any insight you can give me with this.

  5. #5
    Senior Member lakingslayer's Avatar
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    OK I am a dumb A$$!!!!

    My tuning tool was in KPH and not MPH. Now everything is lining up nicely. I still haven't been able to make the TCC lock in 2nd past 50% throttle but I can concentrate more on that next. Sorry for all the cr@p!

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