My 1998 Dodge Ram 2500 4X4 Cummins will not shift into overdrive. Flushed and filled fluid and changed filter, no change. Any ideas?

http://www.youtube.com/watch?v=Gb24f8mWCB8

^Your governor solenoid has no bearing on overdrive or lockup. They are electronically controlled by the PCM. What relay are you saying you replaced? You are probably going to have to get a scan tool on it and see what the truck is doing. See if the PCM is actually commanding it to shift to overdrive, or if something else is keeping it out of overdrive. It could be a broken wire making a bad connection, or it could be the solenoid pack on your valve body.

Thank you. However, I did replace both the solenoid and the shift solenoid/governor. It shift alot better but I still dont have overdrive. When I did the test drive on the highway, I had no change when I used the electronic shift on the shift lever turning the OD on/off. Now I'm really stuck. I replaced the transmission relay under the hood and also the fuse that controls the OD inside the cab. No Change

I have the same problem with my 2000. Did you find a solution? I changed my PCM, my ABS on the rear differential, a used rebuilt trans with 60k miles, and both solenoids in the trans as well after I swapped out the trans. I am lost and don't know what to try next. It is starting to eat a hole in my pocket.

..... Maybe a slim chance, but check the cable running from the shifter all the way down to the point of connection. Visually inspect the mechanics of it, perhaps loose or corroded ground wire, if not able to find you could always add your own, done that to help an engine fire once before added 2 to each side the one on the back of the block we're thinking and breaking.