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Thread: 08 Duramax LMM TCM tune

  1. #1
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    Default 08 Duramax LMM TCM tune

    Hey,

    Question about a TCM tune for my 08 Duramax LMM, I currently have ATP Idaho Rob's ECM tune, what im curious about is there any adverse effects on tuning my Tcm with the Shift point correction calculator for my new tire size?? I have read about other tunes that people have been having issues with the allison acting up after doing so, or should i just leave it be?? my stock tire size is 29.80 new tire size is 32.82 Which calculates out to a 10.16% difference.Am i safe to go ahead and do so??


    Thank you guys!

  2. #2
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    i would not worry about the difference but a quick email to atp will get all your questions answered they have great service if its somethign they left out of the tune they will most likely correct it or if you have upgraded your tire size since purchasing the tune they will most likely recalibrate your tune for small fee. thats been my experience with them they are very helpful

  3. #3
    Lifetime Member killerbee's Avatar
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    Why do you think you need to change your shift points?
    Michael, Systems Engineer 04.5 D-max LLY, Phoenix, Arizona Email
    Custom Tuning Services
    DURAMAX/CUMMINS ECM's TCM's for sale, all years, 20% wholesale discount available
    EFILive's first VGT "Software Wastegate Tune"

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    Hey killerbee,
    Correct me if I'm wrong here, I went up to a 33 inch tire from stock which was a 29-30 I believe , wouldn't correcting the shift points be "easier" on the trans with it bumping them up the 10 percent differance that the efi calculator showed ?


    Quote Originally Posted by killerbee View Post
    Why do you think you need to change your shift points?

  5. #5
    Lifetime Member killerbee's Avatar
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    If your goal is to maintain the same rpm for your shift points, then nothing needs to be done with a tire size change. If you are wanting to maintain the same torque at the shift point, given the longer radius, then you would increase the shift point rpm, and that could, in theory be easier on the drive train.

    As a practical statement, not sure you will notice the change. However the GM factory shift and TCC schedule does have its shortcomings, with areas to be improved in all year groups. Especially the 6-speeds.
    Michael, Systems Engineer 04.5 D-max LLY, Phoenix, Arizona Email
    Custom Tuning Services
    DURAMAX/CUMMINS ECM's TCM's for sale, all years, 20% wholesale discount available
    EFILive's first VGT "Software Wastegate Tune"

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    Thank you for the reply! I was thinking theory wise it seemed it would be better but wasn't sure if it was really worth the effort ? Or if there is any downside to doing such.



    Quote Originally Posted by killerbee View Post
    If your goal is to maintain the same rpm for your shift points, then nothing needs to be done with a tire size change. If you are wanting to maintain the same torque at the shift point, given the longer radius, then you would increase the shift point rpm, and that could, in theory be easier on the drive train.

    As a practical statement, not sure you will notice the change. However the GM factory shift and TCC schedule does have its shortcomings, with areas to be improved in all year groups. Especially the 6-speeds.

  7. #7
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    Is the a40 tcm ok to cal flash if I just use the EFI live shift point calculator and do not change anything else ?


    Quote Originally Posted by killerbee View Post
    If your goal is to maintain the same rpm for your shift points, then nothing needs to be done with a tire size change. If you are wanting to maintain the same torque at the shift point, given the longer radius, then you would increase the shift point rpm, and that could, in theory be easier on the drive train.

    As a practical statement, not sure you will notice the change. However the GM factory shift and TCC schedule does have its shortcomings, with areas to be improved in all year groups. Especially the 6-speeds.

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