Speedo tuning...difference between H0103 and H0122?

[thunder550]

06 LBZ. RPO code for the truck says 3.73 gears. Trans tune says H0103 is 4.10, H0122 is 3.73. Which one is the gear ratio? What's the difference between the two? Shouldn't they be the same?

I'm confused! :D

[ScarabEpic22]

I think I remember hearing that all the TCMs say 4.10s even if the truck has 3.73s or whatever other gears.

[THEFERMANATOR]

All the TCM's are set to 4.10 gears. This has nothing to do with the speedo in the truck, but how the TCM sees the speed reading. The general consensus is leave the TCM settings alone for the speedo as it uses the 4.10 ratio for figuring shift times and torque numbers. By changing it you will essentially change all of your shift times and cause tie-ups which will destroy your ALLISON.

[bballer182]

All the TCM's are set to 4.10 gears. This has nothing to do with the speedo in the truck, but how the TCM sees the speed reading. The general consensus is leave the TCM settings alone for the speedo as it uses the 4.10 ratio for figuring shift times and torque numbers. By changing it you will essentially change all of your shift times and cause tie-ups which will destroy your ALLISON.

Yes X2. Just leave the speedo stuff alone in the TCM. All that stuff in the TCM speedo is for internal calculation and has nothing to do with the speedo reading on the dash.

[thunder550]

Ok so if my speedo is off I need to change it in the ECM then instead of the TCM?

[bballer182]

yes that is correct