Allison 6 speed issues.

[Timothy_james07]

2007 classic gmc sierra duramax. Truck has reverse as normal. As soon as it’s shifted into drive it goes into shift range inhibited. I’ve tried a different tcm. Replaced the internal harness due to leaking into the plug. Gone through the entire harness. The truck will move forward if the harness is unplugged at the transmission. So far what I’ve noticed is that the turbine sensor won’t go to zero when put in drive. It stays at engine rpm so it won’t allow it to complete the shift. It’s not throwing any codes. Hoping someone that knows these transmission can offer some insight. Starting to think whatever in the valve body that applies pressure to the c1/c2 clutch packs is to blame. Thanks in advance.

 

[MrMarty51]

Thank You Timothy for coming to thetruckstop.us
I know not one thing about transmission problems but its possible there might be someone in here that does.
There is one member of the forum that has been going through a lot of health problems and He is mighty sharp on transmission problems so maybe by using the @ sign I can call Him up and see if he is doing good enough to respond.
@THEFERMANATOR
YOU doing okay ?

 

[Timothy_james07]

His post on the Allison was what brought me to the forum after doing some searching. I actually sent him a pm. Hate to hear he’s dealing with health issues. Appreciate it though!