2002 Duramax trans problems. Hopefully electrical

[Alaskasurf]

I just bought a 2002. I knew it had some electrical issues. The gear indicator on the cluster comes and goes. Mostly gone and the trans shifts hard and has a delay on start. I thought it was torque converter drainback at first but pulled codes and seems to be electrical maybe. It has a leak coming out of the gasket between the trans and converter also.
So today I started trying to fix it. First I took the batteries loose and disconnected the TCM cleaned and greased the connections. I think they looked fine. Connected TCM and batteries back, Speedo went to 100mph pegged and stays now . Apparently I just made it worse. I’ve glanced to see all transmission plugs are connected but haven’t taken any off yet to inspect. Then I had to go to work so that’s all I’ve done so far.

Truck has no problems starting 4WD works and switches just the error codes and the hard shifting and delayed start like it’s hunting for the right gear. See codes
Any help or ideas would be greatly appreciated!

 

[TheBac]

Moved to Trans Talk area.

 

[2004LB7]

And how's the fluid level?

 

[Alaskasurf]

And how's the fluid level?

I have filled it up to right below the hot operating level after it warmed up

 

[Alaskasurf]

I took off that pass though connection. The one that talks to the solenoids on the valve body. It was full of transmission fluid at the connection. That could be part of the problem I’m guessing. Also the leak appears to be coming from the top of the extension housing. Probably a crack I can’t see. I need to rep that as well. I’m a little confused on diagrams. Is the output shaft seal on the transmission side of the locking busing or the extension side?

 

[Animals1234]

Do you think its a rebuilt transmission or stock?

 

[Ron Nielson]

Is the output shaft seal on the transmission side of the locking busing or the extension side?

This may answer your question

 

[Bdsankey]

I took off that pass though connection. The one that talks to the solenoids on the valve body. It was full of transmission fluid at the connection. That could be part of the problem I’m guessing.

If there is fluid in the passthrough connector it's time to replace the harness. That can and certainly has caused your codes on other vehicles.

Also the leak appears to be coming from the top of the extension housing. Probably a crack I can’t see. I need to rep that as well. I’m a little confused on diagrams. Is the output shaft seal on the transmission side of the locking busing or the extension side?

There is no output shaft seal on a 4x4 Allison, it is sealed when the transfer case is installed. The transfer case has an input seal to stop fluid from the trans making it's way into the transfer case. There are 2 gaskets between the bell housing and main case (each side of the steel plate the stator support bolts to) as well as a gasket between the main case and extension housing.


Check your vent, it is located on the top of the transmission at the rear of the main case. It looks kind of like a mushroom. I've seen fluid come from that location when overfull or when they get very hot.