TURBOCHARGER GP 1586600 - Caterpillar

(12) for No. 1 clutch. Modulation also takes place between load piston (27) and modulation reduction valve (26) for No. 6 clutch. When the load pistons get all the way against the stops, modulation stops. The pressures in the clutches are at the maximum. No. 1 and No. 6 clutches are now engaged and the tractor transmission is in FIRST speed.Manual Shift (FIRST Speed to NEUTRAL)When the transmission shift lever is moved from FIRST speed to NEUTRAL, downshift solenoid (1) sends pump oil to rotary actuator (3). The downshift from FIRST speed to NEUTRAL is the opposite of the upshift from NEUTRAL to FIRST speed. Rotary selector spool (21) moves from the FIRST speed position to the NEUTRAL position.The position of the rotary selector spool sends pilot oil to selector piston (15). This action drains the pilot oil at selector pistons (10) and (28). Selector pistons (10) and (28) move against the load piston bodies. This action drains the oil between selector pistons (10) and (28) and load pistons (11) and (27). Now, the load pistons and modulation reduction valves move toward the respective selector pistons. Pump oil to No. 1 and No. 6 clutches is stopped by the modulation reduction valves and clutch oil is drained. No. 1 and No. 6 clutches are released. The pilot oil now moves selector piston (15). No. 4 clutch starts to fill. Modulation takes place between load piston (14) and modulation reduction valve (13) for No. 4 clutch. When the load piston gets all the way against the stop, modulation stops. The pressure in the clutch is at the maximum. No. 4 clutch is now engaged and the transmission is in NEUTRAL.Automatic UpshiftsThe transmission speed sensor and the transmission control cause all automatic upshifts and downshifts. The transmission switch tells the transmission control the speed of the transmission that is engaged. The shift lever switch tells the transmission control the gear that has been selected by the operator. The speed sensor senses the rpm of a gear on the output shaft of the transmission. The speed sensor sends this information to the transmission control. The transmission control converts the gear rpm to speed in mph. The transmission control also stores the range of mph for each speed position. The transmission control knows the desired speed position, the actual transmission gear that is engaged and the actual ground speed of the machine. The transmission control will initiate automatic shifts. If the other factors are correct and the ground speed of the machine increases, the transmission control will activate the upshift solenoid at the correct ground speed. As ground speed decreases, the downshift solenoid is activated.The transmission control can not automatically shift into FIRST or REVERSE speeds. The operator must put the shift lever in either FIRST speed or REVERSE. When the machine is stationary and the shift lever is placed in any forward speed except FIRST speed, the machine will automatically start out in SECOND speed and the machine will upshift