584 Int. pto clunking

Reason I ask is we had similiar problem on our 454 when we used it on a Case manure spreader. When ever you backed off the throttle with the PTO engaged on that manure spreader you would hear a rattling noise by the clutch housing. This spreader did not have an over running clutch on the flail beater and it would attempt to over drive the PTO on the 454. When we changed the clutch on the 454, we saw the cause of the noise.

The reason for the noise was the PTO is driven from a spline shaft that fits into the pressure plate. The material in the pressure plate is not as hard as the PTO shaft and after many years of use the mating spline teeth on the pressure plate wear and there is up to 1/4 inch of slop in the connection. In our case the teeth were almost completely worn off.
When clutch and pressure plate were replaced, the noise never occurred again when using the manure spreader.

This could be your problem.
JB2

You can test the slop in your PTO shaft by SHUTTING the tractor OFF with the PTO engaged and then attempt to turn the PTO shaft in both directions and see how much of a revolution the PTO shaft will turn in either direction. Normally there should be very little movement.

I don't think you can check the pressure plate spline teeth from the inspection plate at the bottom of the clutch housing as the throwout bearing blocks the view.

JB2