TM 5-3805-260-24
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
(I) 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. I, 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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