I have a 2000 Ram 2500 (diesel of Course) mostly stock.
124,000 and 47RE Trans. Yesterday just pulling a jeep on a trailer, pulling out the trans would not shift out of first...let off the pedal and tried again...nothing. Eventually got it to go into 2nd but slipped into 1st again. Took it easy in 2nd and finally 3rd and 4th (having probs going into lock-up)
took it to my shop and dropped the pan...ooooo....fluid alright but lots of metal and clutch material...Changed the gov. pressure sensor (reading not good) along with the transducer and filter (also cleaned the output speed sensor). A clean pan and new fluid, still the same. Tried to reset the APPS, but did not help. I realize With the mileage it's prob time for a trans. but has anyone ever ran across this? could it be something i am missing? (also no DTCs) Please Help

 

The "lots of metal" is likely a symptom of clutch failure. Once these transmissions dump metal and friction material into the system the valve body gets contaminated and pressures will generally degrade.

However, just for grins take a good look at the throttle valve cable that runs from the transmission to the throttle bellcrank on the injection pump. If the clip breaks on either end they will not properly set the valve body and pressure will be low. Also take a good look at both of the plastic ends of internal cable that rides in that housing, they can crack and not be noticable until you spring the cracked end a bit.

 

I had nearly the same problem just last week. I had the pan dropped, filters changed, flushed system, etc... No metal/junk in the pan though. After, it wouldn't shift out of first very easily, when it did, it would shift hard, and "hunt" for gears. I pulled the codes from the odometer. The one that showed up was 0720, which has to do with the speed sensors circuit. Anyway, after cleaning the battery cable ends, battery posts, and replacing the speed sensor in the rearend, it runs/shifts better than ever. By the way, my truck is a 2000 like yours. I guess I really should fill out my sig. Anyway, I learned that electrical issues can really affect these trannys. Hope this helps.

 

If you only have first and reverse, then it is either the governor, the 1-2 shift valve in the VB could be stuck or you have burned up the bickdown band or damaged the front servo, ie leaking seals, etc.

You mentioned a lot of "crud" in the pan, I don't knmow how you quantify a lot, but that might be the clutch/friction material from the front band. If you cooked the front band it will only be a short matter of time before you destroy the whole thing.