08 K2 6 Speedo Cal

[GMjohn]

Just a quick question- Downloaded my first 08 K2 6 (LMM Allison)

Under speedo there is two final drive ratios listed-

ratio 3.73(original gears)
Trans 4.10 ??


Vss tire revs

dist 612.23
dist trans 689.63

Why the difference in trans data?? I understand how to calculate the new numbers I need just don't understand why the difference between ECM and TCM.

Anyone have a thought on this??


Thanks,
John-

[capflya]

Not sure why either... when you put the new tire size in and click "commit" or save or whatever the button says it will change both fields to the correct ratio...

[Bill@HPTuners]

Its usually because both the PCM & TCM will have gear ratio information, pcm might say it has 3.73 gears, TCM might say it has 4.10 gears.

Not really sure why GM things this way in all honesty.

[EC_Tune]

You can always check the RPO codes to see what gears are in the truck as well. That will be the final say.

[Programmer]

For speedo/tire upgrade adjustments, don't do anything in the TCM side.

Just work on the VSS Tire Revs per....in the 'DIST' constant. Leave any other constants or tables alone.

[A_W_O_L]

...Could this have to do with 4-HI and 4-LOW on the 4x4's ??? There are different Gear Ratio's between the two...