So I bought my truck back in July.

I got a good deal on it as the previous owner admitted that there was an issue with the transmission that he couldn't figure out and that he was worried that it may be heading for a rebuild.

The truck would randomly slip in and out of gear while driving. It didn't matter what gear you were in, or how fast you were driving. It was more noticeable on highway speeds though.

I was actually ready to do the transmission flush on this truck. I purchased a rebuilt shift solenoid at the same time thinking it couldn't hurt to replace. I'm usually not a fan of replacing parts on a hope and a prayer, but I thought for $100 it was worth a shot while I was under there.

After tons of reading on this forum it became clear that there should be some codes stored as the CEL would come on for a few moments everytime the trans slipped. I finally got around to reading the codes. I had two.....One indicated a problem with the TPS and the other indicated that the truck wasn't all the way in Park when I went to run the test. I thought for sure I was gonna find a code specific to the trans, but no luck. I bought a good TPS, tested it, and threw it in. Apparently this is another sensor that "talks" to the transmission controls. This $50 part fixed the issue 100% immediately!!

I just wanted to share this with everyone and to stress again the importance of checking your codes before you start in on any repairs!

 

The transmission temporarily going into neutral usually ​​​​indicates that the MPLS is failing. You got a code for the trans not in Park so you did get a transmission code.

Yes. The computer uses input from the throttle to help determine what gear the transmission should be in. There is no kickdown cable or linkage. It uses engine sensors. I had the same issue and solution with my Bronco. Replacing the MLPS made it better but it would occasionally still go into neutral and slam back into gear. I fought the issue for almost two years. The TPS eventually set a code. Replacing it seemed to fix it but I sold the truck after a couple months so I don’t know for how long. I did see the truck out on the roads so I assume it was fine.

 

Good on you for getting the problem figured out and not having to deploy the parts cannon. What I learned from this site: the importance of doing the research, knowing your vehicle, and doing comprehensive diagnostic work.

 

Thanks for the feed back as I am sure it will help others.

My 02 Durango would down shift at times when on the high way doing 55 - 65 MPH for no reason.
I did figured it had something to do with the TPS and told the dear when it would happen and what I thought it was.
Turned out to be the TPS and the wiring harness to it.

On the computer controlled cars and trucks it is best to check the computer for codes.
I don't know if my Durango had any as no CEL ever came on.
Thinking the computer saw the TPS go to a down shift signal and why the trans down shifted.
Dave ----