08 Duramax LMM TCM tune

[Bajaguy2]

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!

[Lauder]

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 :)

[killerbee]

Why do you think you need to change your shift points?

[Bajakguy2]

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 ?



Why do you think you need to change your shift points?

[killerbee]

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.

[Bajakguy2]

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.




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.

[Bajakguy2]

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



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.