The pto grinds when engaging with a load because the clutch is not stopping the pto shafts entirely. Without a load, the shaft jumps right in without grinding due to no weight to spin. If you adjust the three pto bolts to spec through the screen hole, it should work properly. You need to shorten the bolts until the gap between bolt head and clutch plate is .060" which is spec. I like to adjust to about .055" to give a little more wear before it needs adjusting again. Check the gap with a feeler gauge.
