We have a JD 6430 with 1 of the rear hydraulic valves leaking down rather quickly. So quickly that you can raise our conditioner and visibly watch the hydraulic cylinders lower while the tractor is running. It's not on the implement side as when you plug hoses into the 2nd valve the hydraulics hold even with tractor shut off. So the question is any advice on where to start to fix the issue. We try to do all but the very worst of our equipment repairs our self but as luck has it this is a 1st. So other than assuming its in the valve I have no idea where to start. It is an electronic valve not a mechanical one as well if that helps. Any help or direction would be very appreciated.