TCM tuning

Mogman

Member
May 3, 2020
311
14
18
Papalote, TX
I have a some questions about TCM tuning.
I have several codes coming in as read on my EFIlive V2 ( U0073, U0121, U0140, P0880, P2536, P0218) at this point I suspect a bad TCM and am waiting for one to arrive.
All the codes are reported by the programmer as TCM codes, So the question is, does the TCM tune have DTCs? I looked at the tune and did not see any.

Gear ratio.JPG
The other questions are about speedometer tuning, I assume one would want them to be the same as the ECM SO

H0102 I think I understand this one as that is the number of notches in the reluctor in the tail section of the transfer case

H0103 now this is where it gets fuzzy, the Final ratio in the ECM was 3.73 the same as the diffs (now 4.92)

H0105 PPK this does not calculate anything like I would think, lets see 40 pulses per drive shaft revolution times the gear ratio of 3.73 = 149.2 pulses per tire revolution times the 424 (now 347) tire revs per K would look like 63260.8 pulses per K, What am I missing here?

H0122 why is this different than the final drive ratio?

H0137 what is the vehicle speed ratio and do I need to change that?

I can assume with some certainty that the TCM has been "tuned" along with the rest of the donor truck.

THANKS!!
 
Last edited:

2004LB7

Well-known member
Dec 15, 2010
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Norcal
All the Allison 1000s in our trucks are that way. GM set all of them up the same and used the ECM to calculate the speed, RPM, etc and sed the info over to the TCM. The TCM has many tables that we don't have access to and/or where never mapped out. Changing any of those perimeters will mess up many of the other tables and can cause bad shifts or make it reacts weird. No reason unless you are very sure of what you are doing to change it.

The only area you should touch, and with caution, is the shift MPH/RPM tables and TCC lock up tables. There may be a few other cells you can tweak but playing in the TCM can be costly.

Since you seem to be new to the TCM tuning, it is good you posted here before going too far. Definitely post up any changes you (plan on) make for us to look over. It's not at all hard but there are a few areas to be aware of. Shift timing for example should only be done with extreme caution. ECM tuning actually plays a bigger part in shift quality then the available tables we have in the TCM
 
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Mogman

Member
May 3, 2020
311
14
18
Papalote, TX
All the Allison 1000s in our trucks are that way. GM set all of them up the same and used the ECM to calculate the speed, RPM, etc and sed the info over to the TCM. The TCM has many tables that we don't have access to and/or where never mapped out. Changing any of those perimeters will mess up many of the other tables and can cause bad shifts or make it reacts weird. No reason unless you are very sure of what you are doing to change it.

The only area you should touch, and with caution, is the shift MPH/RPM tables and TCC lock up tables. There may be a few other cells you can tweak but playing in the TCM can be costly.

Since you seem to be new to the TCM tuning, it is good you posted here before going too far. Definitely post up any changes you (plan on) make for us to look over. It's not at all hard but there are a few areas to be aware of. Shift timing for example should only be done with extreme caution. ECM tuning actually plays a bigger part in shift quality then the available tables we have in the TCM
So I should change the speedo info in the ECM only and just leave the TCM completely alone for now yes?
 
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