I have a 18 year old belt driven 48" exmark with sulky. It has worked great since I bought it used, only complaint is that the belt slips when wet, this last summer it started doing it in dry weather. I checked and filled the transmission grease and it didn't help. Running the machine without the sulky seemed to help somewhat, but belts still want to slip. Aside from changing the oil and greasing the bearings I have not done anything to the mower. I have never (nor have the previous owners) ever changed or adjusted the belts or springs on the machine. Any thoughts on what is going on or how to stop it from slipping would be appreciated.