I'm just making guesses, but is it locked in one of the higher gears? If it was stuck in 4th, that would explain why it would not move very easily. Try selecting 2 or 1 instead of "drive" and see if that helps if you didn't try that already. Like I said though, just a guess. About a month ago, my tranny did sort of the same thing. I went in a gas station, came back out, couldn't shift into drive. Same thing, reverse worked fine. In fact thats how we put it on the flatbed, didnt even use the winch. Dropped it off at the tranny shop cause i had to go back to school, and the guy dropped the pan, pulled the shifting mechanism, didnt see anything wrong, so he put it back together and it shifted fine amazingly. Been running fine ever since. I hope that helps you somewhat, but I know it isn't much to go off of... Good luck.
