ZTR Model 364 53AA1A5L100 Won't Move

I was mowing yesterday and the mower was running fine. But about halfway through my yard I made a 180 turn and when I pushed the levers forward it moved about 12 inches and then just stopped. It didn't make a noise. I shut the motor off and looked under the mower and found that the belt that drives the wheels had come off. After realizing that it hadn't broke I reinstalled the belt. But now when I push the levers forward I can hear a sound from the pump but the mower doesn't move. Any ideas will be greatly appreciated. Thanks