THEORY OF OPERATION - CONTINUED
TRANSMISSION - CONTINUED
Less Than Maximum Signal.
(a) When machine ECM requires a clutch to be engaged, a signal is sent to solenoid. Strength of signal is
proportional to desired clutch pressure.
(b) When signal is sent to solenoid, pin moves right and forces ball toward orifice. When ball moves
toward orifice, flow of return oil into tank passage is restricted. Pressure in chamber increases and oil
becomes reduced pilot oil pressure. Pressure moves valve spool to right against force of spring.
(c) When valve spool moves right, pump oil in pump passage enters clutch passage. Valve spool blocks
flow of oil from clutch passage to tank passage. Clutch pressure will increase due to flow of reduced
pressure oil into clutch passage. Oil in clutch passage also flows through passage into chamber.
(d) Initially, machine ECM sends a high signal to solenoid to fill clutch with oil quickly. Then, a reduced
signal is sent to solenoid to allow clutch to engage smoothly.
(e) Once clutch engages, machine ECM steadily increases signal to solenoid to further engage clutch.
When signal to solenoid increases, pin moves right. Pin pushes ball toward orifice and ball restricts oil
flow to tank passage. Oil pressure in chamber will rise and valve spool will move right. This causes
clutch pressure to increase.