Car wheels won't rotate while in drive or reverse ford expedition 03 transmission fluid seems ok

4X4? How are you measuring the transmission fluid? How dose the transmission fluid smell. All the information you can add will help.

The tranny fluid smells fine I was carrying a 6x12 trailer my first time... I rode up on some grass to back the trailer out and align it with the truck the the wheels wouldn't rotate. As I tried to move it. When I put it into different gears it acts as though it want to do something but it won't move.

Then I was told that I should have put it into overdrive but I didn't before this happened

Put it in overdrive when pullng the trailer? By any chance did you notice the engine getting hot?

Pulling that size trailer should NOT have any affect on the transmission.

No the engine did not get hot all...it was good the car was good. But once I went over the grass... I don't know.

Even if it's not in overdrive

So what do you think happened

Is it possible that the 4 wheel mechanism is stuck and not releasing?