My guess would be a stuck valve somewhere. The only way to know for
sure would be to have a transmission tech do pressure tests. When in
park, if you step on the accellerator the engine behaves as if you are
in drive with the brakes on???? Adding Ford Friction Modifier to the
fluid sometimes frees up sticky valves - but if they are totally stuck
(which it sounds like) I doubt if it will work. I'd count on a
repair/rebuild or replacement