New Holland CX720 Repair Manual page 2777

TRAVELLING - 2WD-4WD SYSTEM Hydrostatic
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Cross Section of Equa-Trac II Control Valve - Off Position
E-T II Valve Operation — Intermediate Position
(Reference figures 10, 11, and 12)
NOTE: References to directions are as if viewing the valve from the rear, facing the front of the combine.
When the rear wheel drive is switched "ON", the system will momentarily go into an intermediate position. The in-
termediate position allows hydraulic fluid under charge pressure to fill the system and wheel motors before full drive
pressure is achieved. This reduces the shock load exerted on the pistons and motor housing.
When the RWD switch in the combine cab is turned to the "ON" position, current is supplied to the solenoid valve (1)
Fig. 10. This energizes the coil and causes the spring loaded spool to move towards the coil. Hydraulic fluid under
charge pressure will flow through the solenoid valve from port (A) to port (B) and to the pressure to engage (left) side
(5) of the selector spool (2) Fig. 11, in the E-T II valve through an external tube.
As the selector spool (2) Fig. 11, moves left, against the pressure of the spring (3) and will momentarily allow hydraulic
fluid under charge pressure to enter both forward and reverse flow dividers (7) Fig. 11, and (17), Fig. 12, through the
feathering lands (16), Fig. 11, on the selector spool. Hydraulic fluid flowing through the upper (9) Fig. 11, and lower
(6) Fig. 12, center channels will keep the check valves (8) Fig. 11 and (20), Fig. 12, closed. The hydraulic fluid will
then flow through the forward (18), (19), Fig. 12, and reverse (12), (13), Fig. 11, pressure supply/return ports to the
wheel motors.
The hydraulic fluid on the pressure to disengage (right) side of the selector spool (2) Fig. 11, will flow through the
drilled passage (14), Fig. 11, to port (C) of the solenoid valve (1) Fig. 10. The hydraulic fluid will flow through the
valve and exit at port (D) and out of the E-T II valve through the case drain. The hydraulic fluid then returns to tank.
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