aktoddc
November 13th, 2013, 09:48 AM
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
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