Here is a little more info that goes with the picture in the last post that may help you.
The hydraulic system uses an open-center design. This means that low pressure oil flows continuously through the valves and lines as long as the valves are in a neutral position. Because of this flow of oil there always must be a way for the oil to return to the reservoir.
The transmission case (M) of the tractor serves as a reservoir for the hydraulic oil. Proper level must be maintained for adequate transmission lubrication and oil supply to the hydraulic pumps (A and B). The engine drives the hydraulic pump from the camshaft drive gear. As the hydraulic pump turns, a low- pressure area develops in the suction line (C). Oil then moves from the transmission case through mesh filter (I) and 25-micron filter canister (G), then on through suction line (C) to the inlet side of the hydraulic pumps.
Oil flows from the outlet side of the hydraulic pump, through pressure line (D) to inlet housing (J). A relief valve (H) limits hydraulic system pressure to a range of 18995 to 19685 kPa (2755 to 2855 psi). If the system encounters sufficient resistance to oil flow due to a heavy load or restriction, the relief valve opens, allowing oil to return to the reservoir. The inlet housing (J) also provides a mounting location for up to three optional selective control valves.
Oil flows from the inlet housing to the rockshaft valve (K). A flow regulating valve controls the amount of oil flow to the rockshaft (L) so it will rise at a constant rate regardless of engine speed. When in neutral, the rockshaft control valve passes oil to the sump. When the control valve is actuated by movement of control lever (E) or by the draft sensing linkage, oil passes to or from the rockshaft cylinder, raising or lowering the 3-point hitch.