1995 Ranger 4x4 Transmission stuck in drive all positions?

I bought a 1995 ford ranger. 4R55 auto . The transmission seems to be stuck in drive throughout all gear selections. will only move forward. even in park, reverse and neutral it seems to be in drive. I drove this truck home 100 miles and got the transmission to even go into overdrive. But as soon as I parked it, it went back to the same problem. No park, reverse or neutral, just drive in all selections.