bought an ih 584 and the pto lever was stuck on when purchased got it all freed up and it engages well and the plunger works up and down, but the pto will only spin at high rpm and can be stopped with a 2x4 with light pressure, put pressure gage on the line coming from the valve body where the hyro filter is according to the book, and it read zero pressure. any leads on where to go next would be greatly appreciated, Thanks