Transmission slips and reverse stopped working

Sounds like you have a bad speed sensor on the ABS. Have the ABS scanned for codes. If you want to test this, unplug one of the speed sensors. The ABS light should come on and disable the traction control system. Then the transmission should work fine. If it does, diagnose the ABS/Traction control system.

Drive it slowly to a reputable transmission shop. There is nothing you can fix yourself.

I thank you have a failed transmission. Take it to a ****** repair shop and have them do a look at it, it will be free at most shops. You must get the problem diagnosed before any repairs are done.

Okay its going to have to be made. What you have is a aftermarket controller. Youll need to take it to a shop that can tap in the system. When they tap in the system and you hook the trailer and tow something Dont be alarmed when the ABS light goes on. Why? because you want that light on if you tow something why? So it doesnt fish tail when you stop.

Judging by your description of when it failed, it sounds as though the transfer case is faulty. A quick and easy way to find out is to remove the drain-plug from the transfer case. The drain plug is located on the rear of the transfer case, opposite the front drive-shaft. The lower plug is the drain. If there is fluid in it, what colour is it? Does there seem to be fine metal in the fluid? I have seen them fail so severely from loss of fluid that "chunks" of metal block the drain hole.

Sound like the planetery gear sprocket broke. Common problem on some of these Dodge Transmissions. Transmission will have to be removed and rebuild or replaced.

If you think it could be the overdrive, try driving with the transmission selector in 3rd, rather than overdrive. If it helps, may have diagnose the problem.

Another option, not sure if that year model had the tow/haul function, where you could set the transmission shift point to change because you were hauling a trailer.

If you can narrow down the problem to the transmission for sure, I would still start with a transmission filter & fluid change, cheaper than rebuilding a transmission.

code p 1870 refers to transmission component slipping
That can be from dirty oil or a clutch pack or band slipping or low oil pump pressure in the transmission
you say that it occurs on highway driving after 2 hours and that slipping will add friction heat to the transmission oil bringing on the oil temp light
take it to an accredited transmission professional service center that works on your make of vehicle , have the oil changed which require the pan removal
at the same time that will allow the adjustments to be done
when reassembled and refilled , have a pump pressure test done

take it to dealer for computer diagnostic check,this sounds like an ECU fault