THEORY OF OPERATION - CONTINUED
TRANSMISSION - CONTINUED
(a) When clutch is fully engaged, machine ECM sends maximum specified signal to solenoid to keep
clutch fully engaged.
(b) Signal sent to solenoid moves pin and ball right. This further restricts flow of return oil from clutch
passage to tank passage. Pressure in chamber increases and oil becomes pilot oil. Valve spool moves
further to right. Pump oil from pump passage flows to clutch passage and clutch will fully engage.
(c) Once clutch is fully engaged, pump oil in chamber and combined pressure of oil in chamber and
spring will equalize. This will cause valve spool to move left to a balanced position.
N OT E
· Modulating valves control engaging and disengaging of clutches.
· These are not simple ON/OFF valves. Machine ECM varies strength of signal sent to solenoid. Signal sent to
solenoid is programmed into machine ECM.
· Since main relief valve will control maximum amount of clutch pressure for all of modulating valves, pump
supply pressure and clutch pressure will be equal when clutch is fully engaged.
(d) In balanced position, oil flow from pump passage to clutch passage maintains desired clutch pressure.
In balanced position, oil flows to clutch to compensate for internal clutch leakage.