PISTON 1489042 - Caterpillar

Shifting from the NEUTRAL position to the First Speed Forward position with a Running Engine
Illustration 4 g02693622
Transmission Hydraulic Controls in the FIRST SPEED FORWARD position
(2) Number 3 clutch solenoid
(7) Flow control orifice
(11) Torque converter inlet ratio valve
(13) Modulating relief valve
(14) Direction selection spool
(18) Selector spool for first speed and for third speed
(19) Pressure differential valve
(20) Load piston
(AA) Speed clutch oil P1
(BB) Direction clutch oil P2
(CC) Torque converter inlet oil P3
(DD) Torque converter outlet oil
(EE) Lubrication oil
(FF) Return oil
(GG) Pilot oil
(HH) Torque converter clutch oilWhen the STIC transmission direction control switch is moved to FORWARD and the speed control switch for the STIC transmission is shifted to first speed, solenoids (1) and (5) are activated and solenoid (2) is deactivated. Solenoid (1) moves a spool. Solenoid (1) also directs oil to the top end of direction spool (14). Direction spool (14) moves downward and pump oil flows around the spool. The pump oil then flows to the Number 2 clutch.Clutch solenoid (5) moves a spool and also directs oil to the bottom of speed selection spool (18). Number 3 clutch solenoid (2) is deactivated. Number 3 clutch solenoid (2) also directs oil from the top end of speed selection spool (18) to the reservoir. Speed selection spool (18) moves upward and pump oil flows around the spool to the number "5" clutch (5).When the shift to first speed forward is made, the Number "3" clutch (2) is opened to the reservoir. The pressure in the system decreases. Springs move modulating relief valve (13) upward. Springs also move pressure differential valve (19) upward until the large orifice