Hung up in gear

My Scott 17/42 riding mower choked down in high grass, when it did it hung up in gear and will not disengage. I pulled it out of the grass and jacked it up, the linkage seems fine and moves through the gears but still it stays in gear. When I jacked the rear end up the wheels turn one in one direction and the other one in the opposite direction. Any help would be appreciated, how do I get it out of gear or what has broken in the tranny?