Allison code list, tq. specs, and other info

[crashz]

You'll have to check that specific code first. However, its most likely a transfer case issue, and a common problem on electronic shift transfer cases is the the encoder motor that shifts the case. But don't start throwing parts at it until you pin-point the problem. Other common issues with the transfer case are speed sensors, dash switches and sometimes the transfer case control mondule. The only "cheap" thing in that list is the dash switch and even then its about $70. The encoder motor is about $500 last time I checked.

[rashworth]

We have a 2002 Duramax automatic four wheel drive short wheel base 3/4 ton truck that we took to the shop to have a gasket or (seal) replaced with the transmission when we took it out of the shop and brought it home it started not shifting...the shift light would flash but would not go into gear...they reset the codes and it worked for a bit, but then started having problems again...they replaced the harness...shift sensor and I believe a couple other things, but the truck got worse and it don't shift at all know...they gave up on it. I spoke with a friend of mine, she said her truck did the same thing (not leaking transmission oil though) just not shifting and the mechanic said it was the solenoid in the transmission...I spoke to the mechanic that was working on the truck they indicated they did not look at this...any ideas...is this a good spot to start looking for problems, is there a way we can check them?
Thanks in advance for your help...

[tcat10001]

Could you please tell me what the problem ended up being on your chevy when this happened to you MINE IS A 02 DURAMAX 2500 HD

[tcat10001]

tcat10001@gmail.com

We have a 2002 Duramax automatic four wheel drive short wheel base 3/4 ton truck that we took to the shop to have a gasket or (seal) replaced with the transmission when we took it out of the shop and brought it home it started not shifting...the shift light would flash but would not go into gear...they reset the codes and it worked for a bit, but then started having problems again...they replaced the harness...shift sensor and I believe a couple other things, but the truck got worse and it don't shift at all know...they gave up on it. I spoke with a friend of mine, she said her truck did the same thing (not leaking transmission oil though) just not shifting and the mechanic said it was the solenoid in the transmission...I spoke to the mechanic that was working on the truck they indicated they did not look at this...any ideas...is this a good spot to start looking for problems, is there a way we can check them?
Thanks in advance for your help...

[race691]

does anyone know which solenoid controls shift between 1st & 2nd gear. My 01 is slamming into 1st on downshift.

[More Power]

As I recall, the Allison can be manually controlled using a Tech II scan tool. A GM tech can go on a ride-along, and select different gears as a way to test the transmission systems. Might be worth a shot.

Secondarily, the Allison has always been a "smart" transmission. The programming learns from the way thee truck is being used to modify its shift scheduling. There are ways to reset the learning process, and have the transmission begin the process again. A search here in this forum for the appropriate keywords should produce more reading and instruction. Jim

[race691]

I actually changed the whole valve body today and it is much worse now than my original problem. I am putting the old valve body back in. When l come to a stop it almost feels as if the truck wants to creep forward