Under load? Unloaded? Is it actually the tractor PTO shaft rotating slower and not a slip clutch slipping?
It has a switch that activates a pto valve.
With 6' shredder connected but not cutting anything it turns about 200 rpm and with the shredder disconnected, it might make a small difference. It was cutting brush fine for a little while until it just bogged down. Now if i put it on the grass, it stops turning.