[bigbagrat]

Aloha to all and holiday greetings from Hawaii! Although I have been visiting here for a long time, I’ve never had to post, since, following the forum guidelines, I’ve researched my problems and found you guys already had answers to everything I’ve needed, until now.

I bought a 2000 Durango (4.7, 45RFE trans) with a bad transmission (hey, the price was right), and had the trans rebuilt at a shop that does all the race work for the local racers. They did a good job, turned it around quickly and the Durango runs fine, except for this code P1781 problem. Code 1781 appears to reference a transmission solenoid. Here’s the situation:

If I am towing a trailer and climbing a fairly steep grade (one thing about Hawaii is most of the roads go straight up and down, no such things as switchbacks here!) and I let the road speed fall below (more or less) 35 MPH, the CEL light goes on and I cannot upshift. For some reason, as long as I keep above 40 or so I can press the accelerator and the trans will shift.

After the code sets, I think I only have second and drive. It’s hard to tell which gears I really have since the transmission is so strong, but I know that I can move the shift lever from Drive to 2nd and get another gear. If I shift from 2nd to 1st there is no change in the transmission. Starting from a dead stop in Drive is a real struggle, but I can shift to 2nd and, although the engine revs up, the trans will move the vehicle. Again, moving the shift lever between 2nd and 1st when stopped doesn’t make a difference. When shifting between Drive and 2nd when moving the trans will “clunk” (technical term…lol!)

I can pull over immediately, clear the code and everything is fine. If I let the Durango sit for a few minutes, like going into a store, it will shift fine for a short while but then the problem returns. Let it sit overnight, the problem is gone.

I have a year’s warranty on this, and this shop has been around a long time, so I’m not worried about finally getting the trans fixed, but I figure many heads are better than one, so if you guys have any thoughts I’d appreciate them.

Thanks for your help!