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Thread: Changing Shift Points

  1. #1
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    Default Changing Shift Points

    Alright I have done a ton of reading about this but am still pretty new to the EFI Live tuning software, and wanted some clarification.

    I bought the V2 to tune my Duramax but have been getting lots of requests to make small changes on acquaintances gas trucks.
    I am tuning my buddies 2013 GMC 1500 with 5.3L AFM and A6 transmission. So far he is extremely happy with the results. I have disabled his AFM (Fuel Mileage increased...) and I have firmed up his shifts via the torque table, which improved the extremely soft shift feel but he is still complaining about the truck going into 6th gear too early in traffic. Can I just alter the shift tables to command the 5th to 6th shift to happen at a higher speed at the TP positions where the early shifts are occurring or is there more that needs to be changed? I will probably change the 4th to 5th shift to be slightly higher as well to avoid a large gap in the shift pattern. I will also have to change the downshift table I imagine.

    He is happy with the rest of the shifts and the new firmness. It is actually pretty annoying when it shifts into 6th in traffic bellow 70 km/h, it becomes fairly sluggish and mashing the pedal when you need to accelerate.
    Normally, on my truck, I would just try it and if it didn't work or I had a problem just re flash the old tune, but because it isn't my truck and I don't get to log large amounts of data on his truck, I wanted to confirm that I could just change the shift points until we are both happy with the shift performance in this specific situation. At some point I will do a full transmission tune using the plethora of information found here but for now we are both kind of learning the gas/trans tuning as we go, changing little things at a time, you know the drill.

    Any Help is appreciated

    Thanks!

  2. #2
    Joe (Moderator) joecar's Avatar
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    Default

    Yes on what you said... do it in increments until you achieve desired results.

    Also, maintain the following conditions at all times:
    Quote Originally Posted by joecar View Post
    PT shift table relationships:

    basic relationships:
    1->2 curve should be above 2->1 curve;
    2->3 curve should be above 3->2 curve;
    3->4 curve should be above 4->3 curve;
    4->5 curve should be above 5->4 curve;
    5->6 curve should be above 6->5 curve;

    additional relationships:
    3->2 curve should be above 1->2 curve;
    4->3 curve should be above 2->3 curve;
    5->4 curve should be above 3->4 curve;
    6->5 curve should be above 4->5 curve;

    this can be summarized as: the curves must not cross anywhere;

    if they cross anywhere, then you will not be able to predict what gear the TCM selects when the operating point hits the cross.

  3. #3
    Joe (Moderator) joecar's Avatar
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    And welcome to the forum

  4. #4
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    Default

    Thanks for clearing up why they can't cross always wondered. The stock ones do so I always wondered what would happen.

  5. #5
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    Thanks for the confirmation and the welcome it is greatly appreciated!

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