MF 283...i dont know the year...(hydraulic pressure valve)has the forward position for front like front end loader, middle for 3 point hitch, and back for rear hydros like disk or wutever.....my question is it OK to switch the valve while the engine is running?? when i go to switch it with engine running u can hear something knocking, like the pressure trying to switch over, and the valve is a little hard to switch, while engine running.....would appreciate any answers thanks..