We have an older 9600 John Deere with a 2 position throttle switch. We would like to go to a 3 position switch like the newer 9600's or a poteniometer where you can adjust the throttle on a dial. What has to be done to accoplish either of them. Is it a solenoid at the pump or is it different ohms through the switch? We need a middle throttle setting especially when unloading. Thanks!