Recently had a pulley that runs the drive belt fail. Put a new pulley and belt on and did a quick test drive around the shop only to find that I didn't have it tight enough, the unit would barely move. So I made it tighter and thought everything was fine after the 2nd test drive. After a week of use I noticed a flat spot on the plastic pulley wheel and had to order a new belt and pulley. I had it to tight!!! Fast forward to now and all the sudden the spreader will slip and not go up hill. I adjusted the belt a little tighter and that didn't help. It will go backwards up a hill no problem. It will move under it's own power on flat ground, but as soon as you go up hill it will stop moving and at a quick glance you can see the fan actually stop moving as well when your going up hill. Could this be the transmission failing? I adjusted the cable that is attached to the forward control and that made the unit faster but didn't help with the issue. Called site one and they had nothing to help.