Hey guys transmission is in limp mode with no CEL. Here is what I know so far. PRNDL lights work on dash. When I'm driving and manually shift into 2nd gear it will engage the underrun clutch pack (engine braking) however it will dissengage it as soon as I shift into any other gear.. And with no CEL its hard to diagnose it.

Anybody know where I should start trouble shooting and does anybody have a good link to the service manual for the transmission?

Edit: Should have specified, its on a 99 c2500 that's sat for a while.

 

Well, I pulled the plug and I have 12v at the harness plug. I also pulled the plug and started it up. CEL still didn't come on. I know the light works because it comes one with the key. However, pulling the harness plug for the transmission and not getting a CEL really worries me. Anybody have thoughts?

 

Alright, I've decided to go ahead and just rebuild the valve body and put new solenoids in it. The most prominent kit I see is the Transgo HD2 kit. I personally would like to just put it back to factory. Anybody recommend a good kit that's not HD2?