Hey all, I'm new here. I've been doing research using this forum but after a few weeks of problems I've decided to request some help.

The problem: Overdrive is not working or is not engaging on my 1996 Dodge Diesel 12V 4x4 Auto.

What I've tried:
Adjusting my TPS - I believe I'm at 1.0V at idle right now. Its been a few weeks since I adjusted it...
Replacing the OD solenoid/TC lock up solenoid assembly.
Hooking up a ground out switch to the OD solenoid as well as the TC lock up solenoid. I am able to lock up the TC but it does not engage the OD.
Holding the brake pedal up while driving.

Other random information:
The truck shifts way too early. I'm usually into 2nd within a few seconds of starting and into 3rd shortly after. I believe I need to adjust my transmission bands.
If I do not use the TC lock up, the TC will lock and unlock randomly while driving.
The OD used to be working but stopped working randomly on a trip back from NY after I ate dinner (turned the truck off and back on)

Can anyone shed some light on my problem? I have read it could also be a speed sensor or transmission temperature sensor problem. Is grounding out the signal from the PCM to the OD solenoid as far as I can go for testing the electronics related to this problem? It seems to me all of these sensors just tell the PCM to send 5V to the OD solenoid or not, right? So am I right thinking I can rule out PCM or sensor electrical problems all by grounding out this signal?

Thanks for any help or thoughts.
Greg

 

the band adjustment wont affect the OD ... I believe your having an electrical issue of sorts .... but that's my $0.02 ..

 

Put a gauge on the OD port and see what it is doing.
I have seen them pop the piston seal.

 

Swap trans relay with ac one. And check crank sensor gap should be at 50 thousandths

 

​​​​​​This ended up being correct!
Many years later I figured out the overdrive clutches were worn out which caused the piston to push past sleeve and tear the piston gasket/seal when the overdrive disengaged. So I was unable to build pressure. I appreciate all of your help and figured I should post my solution!