Trans problem, code 1781

[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!

[2000izusu]

did they replace the solenoids with the rebuild? if you have alot of miles on the odo and it was used for alot of in city driving (example newspaper route,shifting all the time), they should of done the solenoids with the rebuild! but alot of rebuilders cut costs and put them (the old solenoids) back in if they ohm out good.

if the fluid is pink i think we can rule out dirt in the solenoid plunger due to the fresh rebuild! just topics for thought.

if it is the solenoid that took a dump i would replace the others as well! (will probably cost more since the others will probably ohm out fine!)

solenoid is nothing more than a relay with a plunger that directs the flow of atf +4 in the trans. so it is very possible that the solenoid/relay is not passing good voltage because of worn contacts!

mike

[xeroinfinity]

That code - P1781 Engine Torque Signal Circuit

Sounds like a short in the wire harness it can happen during rebuild, or a bad TSC.

I'd have the shop that rebuilt it look at this asap, you could damage the clutches you just replaced.

Hope that helps and welcome to AF.

[bigbagrat]

Thanks for the responses! I'll take this info down to the shop and see what they do.