2006 Duramax Allison - 2 Different Final Drive Ratios (v3.4)

[zstripper2k]

This is the first Allison trans I have tuned on so.......

I'm attempting to adjust for different tire height and noticed in the calibration section of the speedometer there is a ECM and TCM field. The ECM labeled as "Ratio" shows 3.73 and the TCM labeled as "Trans" shows 4.10. The dilemma I'm running into is when I use the Gear/Tire Wizard under Edit the gear ratio under Current is 4.10. When I make my tire size adjustment, enter 4.10 in the gear ratio box and leave Adjust Speedometer and Scale Transmission checked then click adjust, it is changing the ECM "Ratio" value to 4.10 also. To go around this I tried the wizard again but left Adjust Speedometer unchecked then clicked adjust, then manually adjusted the VSS Tire Revs and left the final drive ratios at 3.73 and 4.10. The stock VSS values were slightly different so I used the same multiplier I calculated on both values. Am I doing this right or over thinking it?

[zstripper2k]

So I just went ahead and wrote the config and everything seems to be good, actually great. The truck has 315/70R17s (stock was 245/75R16) and the shifts were really delayed and jerky on accel and decal. WOT shifting seemed like it didn't know where it was. Shifts are silky smooth and quick now. Verified with GPS speedo is dead on all the way to 90mph so far.

Does anyone have any input on Torque Management adjustment for the Allison? There seem to be a lot more parameters than the early 2000s 4L60/80s I've messed with (all my personal vehicles). I've downloaded a few tunes from the repository to see what values people are changing and there are a lot of tables on both the engine and transmission side that are being modified. I can kind of understand why some of the values are being changed but would like to see if anybody would volunteer any pointers.

[Picklito]

I had same issue with 3.73 in the ECM and 4.1 in the trans. I let the wizard do it's thing and we'll see how it goes.

Addendum: I just checked and it does now say 4.10 in both places. Truck has GT4 code so should be 3.73, and doing the math for tire/rpm/mph it checks out as a 3.73. Weird.

[Picklito]

I went back and put 3.73 in for both ECM and TCM, and reflashed with the correct tire size. Speedo is nearly perfect. Still a mystery why the stock tune has 3.73 in ECM and 4.1 in TCM.