This information pertains to the PTO unit of IH tractor models 706-1586. The PTO unit on these tractors is a self contained assembly bolted to the rear frame of the tractor. The power is transferred to the unit by a constant running shaft driven by the clutch pressure plate. The constant running shaft powers a hydraulic pump driven by the input shaft of the PTO unit. ( this pump is self contained in the unit and only supplies pressure to the pto unit)The hydraulic pump supplies oil pressure to a control valve inside the PTO unit housing. When this valve is activated , it directs oil pressure from the pump to a hydraulic piston that when pressurized engages a clutch pac which drives the out put shaft.This unit can be removed from the rear frame of the tractor for repair. The complete unit needs to be removed,it cannot be disassembled on the tractor. Removal requires draining the transmission/rear housing oil. Removing the 3PT hitch upper link bracket/cover allows access to aid in shaft alignment.The unit can be pulled back enough to disengage the drive shaft ,care should be taken to not damage the oil sump tube which angles down towards the bottom of the rear frame housing. The complete unit can be removed from the tractor for repair. Using 2 of the long bolts that held the unit in the tractor ,screw them into the 2 top rear threaded bolt holes( they will be sticking out the back while unit is still in the tractor) . They will act as legs to stand the removed unit on them and the 540 output shaft. The input shaft will be pointed straight up. Now it will be easier to repair the unit. JLS