View Full Version : OS reflash?

January 11th, 2011, 12:06 AM
I have a pair of Allison TCMs, one is a 00 (not Chevy truck) and the other is an 01. Is it possible to reflash them to the 04-05 OS so they will run a trans with the G solenoid (main pressure modulation solenoid)? Or, will I have to have a stealership do it for me?

January 11th, 2011, 09:11 AM
Depends upon what part numbers they are. SOME 01 GM TCM's cannot be updated to the later OS's as they have a different board in them(mostly these came in 8.1L trucks is what I was told), and I'm pretty sure your 00 won't flash either. When I needed another TCM this is what I was told, but don't know it for certain. But why are you worried about using the G solonoid? You can just leave it unplugged and forget about it as it doesn't have to be there. It was used on the LLY+ trucks to drop the line pressure at idle to 7 PSI to reduce trans temps. As soon as you touch the throttle the G solonoid would have the powe cut to it and ramp main pressure back up.

January 11th, 2011, 06:10 PM
Hmm, if thats the case I may just have my buddy at GM flash it for the latest code it will take and call it good until I can get a Gen IV TCM setup worked out. The trans I am using is an 07 6 speed, but at the moment I dont have a Gen IV TCM, and finding one that is flashed for TPS input may be problematic. Every one I have ever seen, GM or MD, is clearly labeled "Throttle Input: J1939" :( So, I guess until then I will have a 5 speed with no main pressure modulation...

Oh, in case your scratching your head and saying "Wuuuut????", this is all going behind a 12V Cummins :D

January 11th, 2011, 06:58 PM
You could get a SUNCOAST 6 speed conversion valve body and TCM, then hook that up with the DESTROKED kit and have 6 speeds that way. Little pricey, but it would be the only way right now with whats available to pull it off. The DESTROKED kit is simply a PCS fule box that they had software written for that can communicate in J1939 and J1850 for teh ALLISON TCM so it can receive the needed J1939 TPS signal and J1850 tow/haul and OD/LO signals.

January 11th, 2011, 07:29 PM
A little pricey? :p Yeah, I would say so :D

Before I did all that I would just score the TCM, ECM, BCM, and harness from a wadded up DMax truck and hack it in. In theory, although the DMax ECM would throw all sorts of codes, it should still send it's data to the TCM and actually work. Kinda cumbersome having 3 ecu's, with two that aren't really doing much, but I think it would work....

For now, Im gonna stick with the older 5 speed TCMs and get it running. I will ponder refinements later.