Manual selector value

TM 9-2520-249-34&P

prevent full main pressure from entering the valve bore

(3) Flow value. Main-pressure oil enters

(fig. 2-2).

the valve bore at the top of the valve, and also through

(9) Left brake signal valve. Main-pressure

an orifice which feeds another orifice at the bottom of

the valve bore. In neutral operation, pressure is equal

oil is blocked at the valve body bore by the signal valve.

at both ends of the valve. The bottom portion of the

When the valve is allowed to move downward by

valve has a larger area than the top portion and thus,

movement of the brake apply cam, coolant oil is

the valve is held in the upward position. Movement of

directed to the left output section (fig. 2-13). The

the flow valve is dependent on the pressure differential

function and performance of this valve is the same as

caused by a heavy oil flow across the upper orifice.

that of the right brake signal valve (a(5), preceding).

(paragraph 2-38d).

(10) Steer valves. Main-pressure oil is

(4) Manual selector value. Main-pressure

supplied to the right and left steer valve bodies. When

the valves are in the no-steer position, main-pressure oil

oil enters the selector valve bore cavity and charges the

is blocked by the steer regulator valves. However, main

upper passage in the selector valve. In neutral, main

pressure can enter through bores at the steer valve

pressure is blocked at all valve ports except the reverse-

location and leave through the right- and left-forward

i signal port which is blocked by a ball-type check valve.

feed passages. The oil enters the drive relay valve and

Thus, in neutral, no forward- or reverse-range clutches

leaves through the right and left drive feed passages

are charged.

and enters the steer relay valve. The main-pressure oil

(5) Right brake signal valve.

Main-

is then directed through the right and left geared steer

pressure oil is blocked at the valve body bore by the

clutch apply passages to charge the respective steer

signal valve. When the brakes are in the release

clutches. Figure 2-13 illustrates the engaged steer

position, spring pressure holds the valve against the

clutches.

brake apply cam. When the brakes are applied, the

b. Converter-in Circuit (yellow).

cam allows the spring to move the valve upward. In this

(1) All oil in excess of that required to

position, the exhaust port is covered and main-pressure

maintain main pressure passes into the converter in line

oil is directed to the left end of the brake coolant air

leading from the main-pressure regulator valve. When

valve, forcing it closed. This stops the air supply to the

pressure in the converter-in line exceeds 100 psi, the

brake coolant pump which causes the pump to draw

converter pressure relief valve open and allows oil to

cooled oil from the transmission sump and direct it to

escape to the power train sump.

the right output section (fig. 2-13).

(2) The converter-in circuit passes

(6) Main-pressure regulator valve. Main

through the lockup shift valve. When the valve is

pressure oil enters the valve bore, surrounds the stem

upward (lockup engaged), converter-in oil must flow

and flows through a ball check valve in the stem to an

through an orifice. When the valve is downward (lockup

area above the valve. This area is also connected with

released), converter-in oil flows unrestricted to the

main-pressure oil through an oil-escape orifice. The

torque converter. The purpose of directing oil through

pressure on the top of the valve pushes the valve

the lockup shift valve is to decrease the oil flow to the

downward. and compresses the spring proportionately

converter during lockup operation (para 2-38c(2)).

to the amount of oil pressure applied at the top. When

c. Pitot Circuit (green and white). Pressure in

the hydraulic and spring pressures are in balance, main

oil pressure is regulated. If the oil supply to the valve

the pitot circuit is produced by rotation of the fluid

becomes too great, or if the oil is cold and does not flow

velocity governor and, therefore, varies proportionately

easily, the valve will move down-ward far enough to

with turbine speed. This varying pressure is directed to

uncover the exhaust port. This will allow the oil to return

the downshift inhibitor valve and the lockup shift valve.

directly to the sump. The main-pressure regulator valve

(1) Downshift inhibitor valve.

Pitot

directs main pressure oil to the lockup shift valve, left

pressure enters at the right end of the downshift inhibitor

brake signal valve, and steer valves.

valve. During idle in neutral gear, pitot pressure

(7) Lockup shift valve. Main-pressure oil

(proportional to turbine speed) is not great enough to

is blocked at the valve body bore by the middle portion

overcome the return spring at the left end of the valve

of the valve stem. Movement of the lockup shift valve

plunger. Increased pitot pressure, greater than that

is dependent on pitot pressure (c(2), following).

produced at idle, is required to move the valve plunger.

(8) Lockup regulator valve. Lockup oil

Movement of the plunger, however, will not prevent a

pressure is regulated by movement of the valve. An

shift from neutral.

increase in pressure into the valve bore goes through

the valve orifice to the end land, forcing the valve

against spring pressure and blocks off the intake port to

2-14