TUBE AS 1871273 - Caterpillar

LOW SPEED
Illustration 7 g06070493
Left travel motor (LOW SPEED)
(4) Travel speed solenoid valve
(5) Pilot line
(14) Pressure sensor (drive pump)
(18) Passage
(20) Displacement change valve
(23) Counterbalance valve
(25) Left travel motor
(26) Swashplate
(27) Motor rotary group
(28) Passage
(29) Swashplate control piston
(30) Passage (return oil)
(49) Drive pump
(50) Pilot pump
(56) Travel speed control switch
(58) Left travel lever/pedal
(A) Indicator for HIGH SPEED
(B) Indicator for LOW SPEED
(C) Machine ECMWhen travel speed control switch (56) is set at the LOW SPEED position, an electrical signal is sent to machine ECM (C). The engine and pump controller does not energize travel speed solenoid valve (4) and pilot system oil pressure flows through pilot line (5) to displacement change valve (20). The spool in the displacement change valve shifts downward. A portion of the oil flow from the drive pump in passage (18) flows through displacement change valve (20) and passage (28) to swashplate control piston (29). As a result, swashplate control piston (29) moves swashplate (26) to the maximum displacement position. At the same time, the oil that acts on swashplate control piston (29) flows into the case drain of the travel motor. One rotation of