I have a 20 year old Craftsman garden tractor that has been a great machine. Today while mowing, the tractor stopped moving. No forward or reverse. I checked the belt, brake,axle keys...all appear to be fine....when I have the rear of the tractor lifted off the ground the wheels barely turn in forward or reverse and I can stop them by just touching either tire. I hear what I believe is a noise coming from inside the transmission when I rotate the right side rear wheel with the engine off. Any ideas would be greatly appreciated. The tractor owes me nothing but still runs great. Thank you