TM 5-3825-226-24
NEUTRAL WITH ENGINE NOT RUNNING
The basic components of the oil system for the
hydraulic controls are: oil reservoir (18), magnetic
strainer (16), oil filter (13), oil pump (15), pressure
control valve (1), selector valve (19), torque converter
(4), lubrication relief valve (8) and oil cooler (7). All the
oil passages are inside the cases except the supply lines
for the oil pumps and the lines to and from the oil cooler.
The hydraulic controls have a pressure control
valve (1) and a selector valve (19). The controls are
fastened to the clutch housings and are completely
inside the transmission case.
Valve spools (20) in the selector valve are
connected together and work as a unit. These spools
send oil to the speed clutches (No. 1, No. 4, No. 5 or
No. 6 clutch). Valve spool (14) in the selector valve
sends oil to the direction clutches (No. 2 or No. 3
clutch). One speed clutch (No. 1, No. 4, No. 5 or No.
6 clutch) and one direction clutch (No. 2 or No. 3
clutch) must be engaged to make the machine move.
The differential and safety valve (6) is in the
pressure control valve. This valve causes a difference
in pressure in the speed and direction clutches, keeps
the machine from moving if the engine is started in any
speed except NEUTRAL, controls the flow of oil to the
direction clutches, and is a check valve for the chamber
behind load piston (3).
With the engine not running, the pump is not
being turned and there is no pressure oil in the system.
The springs for valves (2) and (6) and load piston (3) are
extended and the valves and load piston are against
their stops.
This chart gives a description of the function of
the valves in the hydraulic controls.
VALVE
FUNCTION
Controls the increase of pressure in the direction and speed
Modulation Relief Valve (2)
clutches to gradually engage the clutches.
and Load Piston (3).
Does not let the system pressure be more than 310 psi (21.80 kg/cm2) (2137 kPa).
Ratio Valve (5).
Does not let the oil going to the torque converter have a
pressure of more than 115 psi (8.08 kg/cm2) (793 kPa)
Controls the pressure difference between the speed and direction clutches.
Keeps oil from going to the direction clutches if the machine is
Differential and Safety Valve (6).
started in any speed except NEUTRAL
Controls the flow of oil to the direction clutches.
Opens a return passage to release the pressure from the right end of
the load piston during a shift.
Direction Selector Spool (14).
Opens the direction clutches to pressure oil or to the reservoir.
Speed Selector Spools (20).
Opens the speed clutches to pressure oil or to the reservoir.
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