2002 2500HD Allison Software Update

[mikedegan78]

I had an issue with the Allison that had a harsh downshift from 2-1 (TSB 02-07-30-020) I have access to a Tech 2 so I reprogrammed the TCM with the latest software version from GM. Upon doing so it has radically changed the shift pattern. It doesn't engage 5th gear til 50+MPH and the TCC will not engage in anything other than 5th gear. I have tried to revert to the old programming, but I am unable to select it from GM as the options are greyed out. Am I SOL? or does someone know how to back up the software versions on the PCM and TCM? Thank you for your assistance.

[gmtech4]

sorry ,bud ,but you answered your own question,

 

 

SOL

[Shaners]

That seems more like the shift pattern when in tow/haul mode or even more like the shift pattern for when the engine and tranny are stone cold.

[scooby5121]

Hi ,Mikedegan78

If you live near Toronto, Ontario I could help you out.... Their is a guy who writes the whole program for the computer for the engine and transmission..

He does everything you could possibly imagine. He is the computer. Burt Raising is his name of BR Powersource in Oakville. He has customers who line up for an appointment.

He is on the web, if you live within a reasonable distance he can fix it while you watch his computer skillls. VERY HIGHLY RECOMMENDED.

Scooby