Hey everyone i just bought this 94 dakota 3.9 4 speed auto with 148k on the clock. The transmission wont shift into overdrive. I have checked the electrical connections, the overdrive switch, replaced the speed sensor and it still wont shift into overdrive. It looks like the transmission has some fluid comibg out of the speed sensor but im not sure. I checked the fluid and its completely full. Any ideas on what is next? Also no check engine lights. Transmission shifts smooth in all other gears. Thanks!

 

Hi vitalssj Let me save you the last years worth of effort for myself. I bought a 94 3.9 with similar issues and now had 140600, it had an EGR code, I replaced it.
After a lot of work I am glad I did as it doubled gas mileage, I could not figure out the transmission with many conversations and a couple transmission oil changes the second one part of a service.

Here is the solution. I took it into a shop and asked them to check that the engine was running correctly. I would not provide any other information to them when they asked mainly so that my perceptions and descriptions did not divert them from doing what they know. Just keep telling them you want to know that it is running correctly resist giving them anything else. This way you eliminate the engine as a source of the problem.
They checked it out the motor was fine and the transmission was slipping. I had been using all kinds of descriptions and slipping was never one of them. What I called jumping was what they called slipping. They recommended the tranny shop I was taking a leap of trust as I had been burned by the last shop who "serviced" it
Anyway I took it to a good tranny guy who drove it with me and his impression was that it was not so much slipping as it was losing internal hydraulic pressure from either a bad pump or bad seals. The solution is to rebuild with all updates.
I will get that done next week.
Good luck.