P O W E R T R A INT R A N S M I S S I O N H Y D R A U L I C C O N T R O L SStarting the Engine(Transmission in a Speed and Direction)TM 5-3805-258-24-1S Y S T E M S O P E R A T I O NTRANSMISSION HYDRAULIC CONTROLS(Engine StertedIn First Speed Forward)6.No. 5 clutch.13. Modulation relief valva.7.No. 4 clutch.14. Pressure differential6.No. 6 clutch.valve.10. Speed selection spool.16. Ratio valve for torque11. Load piston.converter.12. Tranamiaaion neutralizer17. Direction selection spool.valve.When the engine is started with the transmissionselection lever in either FORWARD or REVERSE,the operation of pressure differential valve (14) pre-vents movement of the machine.As pump oil goes through the small orifice at theleft end of pressure differential valve (14), it starts tofill the chamber. However, when direction selectionspool (17) is in either FORWARD or REVERSE,the position of the spool opens a passage from thechamber to the reservoir, through the large orifice atthe left end of the valve.As the pressure in the system increases, the pres-sure in the chamber at the left end of pressure differ-ential valve (14) does not increase. Since the pressurein the chamber does not increase, the valve can not16. No. 1 clutch.E. Pressure tap for speed19. No. 3 clutch.clutch (Pi).20.No. 2 clutch.F. Pressure tap for direction22. Flow control orifice.clutch (P2).D. Pressure tap for converterinlet.move to the right against the force of the springs.Since the pressure differential valve does not move tothe right, pump oil does not go to a direction clutch.Direction selection spool (17) must be moved tothe NEUTRAL position, to close the passage to thereservoir,before pressure will increase in thechamber at the left end of pressure differential valve(14). At this time, the increase in system pressure isfelt in the chamber of valve (14). As the pressureincreases in the chamber, the pressure differentialvalve will move to the right, against the force of thesprings. This puts pressure differential valve (14) in aposition to let the pressure increase in the directionclutch circuit when direction selection spool (17) ismoved from NEUTRAL.3-47
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