Service Manual

THEORY OF OPERATION

5xi Series Tractor Hydraulic Service Manual 2 - 5

The power steering and hydraulic lift circuit are also operated by the charge pump. When the lift control valve is

moved to Raise or Lower position, the charge pump output is diverted to one of the hoses attached to the lift

cylinder. The other hose is connected through the lift valve to charge pressure hose leading to the oil filter,

permitting bleed-off of oil on that side of lift cylinder’s piston. Implement relief valve located in control valve

(manual steering) or power steering valve regulates lift system pressure at 700-800 PSI (48.2 - 55.2 bar). When

this valve opens, excess oil is bled off into the charge pressure hose leading to the oil filter.

NOTE: Lift valve noise is normal on manual steering units.

(A) Charge Pump

(B) Transaxle Sump

(D) Lift Valve

(E) Lift Cylinder

(F) Steering Cylinder

(G) Power Steering Valve - With 725 PSI (50 bar) relief valve

(H) Charge Pressure Test Point: 30-90 PSI (2.1 - 6.2 bar)

(I) Lift Pressure Test Point: 725 PSI (50 bar)

Red = Oil Under Pressure

Blue = Oil Not Under Pressure

Green = Suction Line

NOTE: Pressurization of lines at lift/steering

cylinders reverses with change in valve

actuation.

HYDROSTATIC TRANSMISSION FLOW DIAGRAM WITH POWER STEERING