Transmission Problems

I have a 1989 xj that I have been rebuilding and the other day somebody moved my truck, and lost the brakes, so instead of using the emergency brake jammed the truck into park while reversing to stop the jeep. I took it for a spin afterwards and the truck goes in reverse fine, its in the forward gears that it doesn't seem to have any power. It goes forward, but it takes a lot of time to pick up speed. I didn't really try going over 35 miles an hour, but does it seem like my transmission is gone? I don't hear any grinding noises or anything.

Thanks in advance