Stuck in nuetral and a huge clunk

[kopylov]

My car had a small whizzing sound for some time (don't know if it has anything to do with the current problem). As i was going home one day a huge clunking started it increased with the speed and decreased as well. Afraid for the car and my life i pulled over and called a tow truck. When the guy was unloading my car it was stuck on the ramp even in neutral. After much frustration we started the car and put it in reverse. i Had to give a good amount of gas for it to "break loose." a huge clunk was heard. While rolling the car i can roll it forward but it is impossible to do it backwards.

The transmission was changed about 5 years ago with a brand new with the previous owner, that is why i am skeptical of it being the transmission. Could it be the diff? Any feedback would be greatly appreciated.