P O W E R T R A IN
T 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 S
Starting the Engine
(Transmission in a Speed and Direction)
TM 5-3805-258-24-1
S Y S T E M S O P E R A T I O N
TRANSMISSION HYDRAULIC CONTROLS
(Engine Sterted In First Speed Forward)
6. No. 5 clutch.
13. Modulation relief valva.
7. No. 4 clutch.
14. Pressure differential
6. No. 6 clutch.
valve.
10. Speed selection spool.
16. Ratio valve for torque
11. Load piston.
converter.
12. Tranamiaaion neutralizer
17. Direction selection spool.
valve.
When the engine is started with the transmission
selection 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 the
left end of pressure differential valve (14), it starts to
fill the chamber. However, when direction selection
spool (17) is in either FORWARD or REVERSE,
the position of the spool opens a passage from the
chamber to the reservoir, through the large orifice at
the 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 pressure
in the chamber does not increase, the valve can not
16. No. 1 clutch.
E. Pressure tap for speed
19. No. 3 clutch.
clutch (Pi).
20. No. 2 clutch.
F. Pressure tap for direction
22. Flow control orifice.
clutch (P2).
D. Pressure tap for converter
inlet.
move to the right against the force of the springs.
Since the pressure differential valve does not move to
the right, pump oil does not go to a direction clutch.
Direction selection spool (17) must be moved to
the NEUTRAL position, to close the passage to the
reservoir,
before pressure will increase in the
chamber at the left end of pressure differential valve
(14). At this time, the increase in system pressure is
felt in the chamber of valve (14). As the pressure
increases in the chamber, the pressure differential
valve will move to the right, against the force of the
springs. This puts pressure differential valve (14) in a
position to let the pressure increase in the direction
clutch circuit when direction selection spool (17) is
moved from NEUTRAL.
3-47
