Hello all, I have a Simplicity Regent EX lawn tractor. It has 137hrs on it and began throwing the drive belt off of the transmission suddenly. I have replaced the belt and confirmed it was the right belt from the dealer and it continues to lose the belt off of the transmission. I have inspected all pulleys and confirmed I have routed it correctly. No problems found. The belt just seems too loose when the parking brake is engaged. The tractor will move fine but when I stop and put parking brake on with engine running it throws the belt right off. Please help I don't know what else to do. Everything is tight with transmission mounting. Maybe a shorter belt??