Q: It will not go in to park or shift in to any gears.

It was pulled out of a parking lot and almost immediately bad grinding/clanking??? metal sound. Lost park and all gears will not engage into park or go into any gears. Towed it home in neutral (even though it all seems like neutral) Once it was in spot went to put shifter in park position and it made grinding gear sound. Like the transmission was moving internally when it shouldn't be as it was stopped. I guess this is leading me to suspect transfer case possibly or looking for any helpful input. It's a automatic AWD transmission no 2wd or any other switch it's just a awd model. If transfer case is suspected is it a replace the whole unit or is there parts to test/diagnose replace in it. I was not the one driving when it happened so description is second hand unfortunately.

Thanks in advance
98 mercury mountaineer, My car has an automatic transmission.