Well this isnt a need help but to share my solution, I have 96 Ram 2500 4x4 it had a shifting issues that would keep it locked up in first , I could manual shift it manaul but would not shift in Drive , once in awhile if let off gas peddle it would shift .
Anyway I changed out the pressure regulator and pressure regulator sensor located inside the trans on the valve body ( you can see it when you drop the pan ) replaced them plus a fluid change and filter, she rolls like a new vehicle . hope this can help someone. 150 in parts and hr labor time . also I recommend if you dont have a external trans cooler install one the cost about 80 bucks