The flow control valve I listed should solve the problem of damaging the pump. The only thing I am not sure about is that when he raises the planter it may rob all the fluid from the the blower and cause it to loose vac and drop the seeds out of the cells causing the planter to plant several feet till the seeds are picked up again. That is why I suggested talking to a JD mechanic. But as far as running the vac with an open flow system, as long as the flow control valve will handle all the tractor flow (rated GPM) and the excess flow port of the flow control is routed back to the tractor return, there should be no way to hurt the tractor running a hydraulic motor as long as it has a transmission cooler. The flow control valve simply lets the excess flow (what the motor does not need to turn it the proper speed) flow back to the return, just like putting a hose from the outlet to the inlet of a remote outlet and pulling the valve to the on position.....oil just flows freely around the circuit. We have used these valves in a lot of different situations, both on open center systems and on closed center where the tractor flow control controls the volume of oil to the flow control valve that is operating in essentially an "open" circuit.

John