1997 mustang Gt auto trans won’t move in drive

[5.0Moses]

I have a 1997 mustang Gt with an automatic transmission. I have been noticing that when I floor it, it just downshifts, revs, and doesn’t go anywhere for a few seconds, then hits. Just the other day I was waiting at a stop light and it wouldn’t move, just very slow as if it was idling in gear. It just revs and doesn’t go anywhere. And reverse works. Drive, 1st, 2nd don’t move. I don’t know much about these transmissions. I would 5 speed swap, but I just wanna sell it. Things that are done to it mechanically wise is pi-intake manifold swap and cold air intake.