1998 Mercury Marquis Wheels locked

No warning, got in car to back out, sounded like I ran over something and car stopped abruptly, would also not go forward without loud clank. Putting car in forward and reverse would bring down engine rpm under load. In moving drive selector back and forth showed that I could not put it in low range.
For the last 2-3 months have had problems taking car out of park unless heavy force on break, and jiggling range selector in the Park mode.