Setting Axle Gear Ratio and Speedometer Calibration

[aktoddc]

I have a question related to setting axle gear ratios and speedo settings.
Some background-
I have a 94 hummer H1 that has a 2006 Express van 2500 Duramax LBZ drivetrain swapped into…this is the 4l85E trans, not the Allison. The ECM is a E35, the TCM is a T42.
So, my speedometer is reading about 12.7% high according to an Edge CTS…and I believe that this is causing the trans to shift slightly early in each gear, since the mph calculation is in error.
Here are the following speedometer settings-

ECM / TCM
H0103 Final Drive Ratio
4.88 / 4.88
H0122 Axle Ratio
No Parameter / 1.00
H0136 Tire Revs per mile
598.2 / 545

So what is the difference between H0103 & H0122? Should they be set the same? Why is the axle ratio set at 1.00? I read somewhere that H0103 is used by the ecm/tcm on the Allison to calculate shift points and should not be changed. Is this the case with the 4L85E as well?
The H1 has portal hubs( gear reduction), so the axle differential gear is 2.73 but the final gearing at the hub/ wheel is 5.46. Which number should I use for the H0103 & H0122? Does the ECU & TCM just use these for mph calculations or is it using the data for calculating other things, like engine torque?
I have the tire revs per mile number from the tire manufacturer. Should I just enter that in? Also, once I get the correct numbers plugged in and the speedo is correct, do I have to go into the shift point correction calculator and alter those numbers as well, or will it automatically already be done with the speedo correction?

Thanks for any input you can give me.

-Todd

[THEFERMANATOR]

From my understanding the 4L85E uses actual vehicle speed to determine shift points, so if you correct the speedo it will change all of your shift points. Not sure if the T42 does it, but I know that the software has a correction tool for some PCM's to correct all of your shift points when you make a speedo correction. I would set the ECM settings to actual final gearing, and make everything read correctly. Then go through and change your shift points by whatever percent to bring them back to stock(or set them where you want them at).

[aktoddc]

From my understanding the 4L85E uses actual vehicle speed to determine shift points, so if you correct the speedo it will change all of your shift points. Not sure if the T42 does it, but I know that the software has a correction tool for some PCM's to correct all of your shift points when you make a speedo correction. I would set the ECM settings to actual final gearing, and make everything read correctly. Then go through and change your shift points by whatever percent to bring them back to stock(or set them where you want them at).

Ok, so should I make the changes in the TCM as well, or just in the ECM?

[THEFERMANATOR]

Ok, so should I make the changes in the TCM as well, or just in the ECM?

With how the 4L80E and it's associated controls work I would think you would want to correct both.