Section II. OPERATION OF HYDRAULIC SYSTEM

TM 9-2520-249-34&P

These covers are machined, magnesium-alloy castings.

2-27.

Oil Transfer Plates

The right end cover includes a mounting pad to

a. Description.

accommodate the speedometer drive cover.

(1) Oil transfer plate (55, FO-10) is

b. Function.

located under the main pressure regulator valve body

(1) Sump cover (76, FO-11) permits

assembly. It is a magnesium-alloy casting in which

access to the brake coolant pump assembly.

numerous oil channels have been machined or drilled.

(2) Housing cover assembly (36, FO-13)

(2) Oil transfer plate (18, FO-13) is

provides a mounting for oil transfer plates, brake and air

located under steer valve (54, FO-12) and control valve

valve controls, control valve body assembly, and steer

body (7) assemblies. It is a magnesium-alloy casting

valve body assembly. Removal of the housing cover

having numerous oil channels. Separator plate (130)

permits access to components in the bevel gear

separates oil transfer plate (18, FO-13) and steer valve

housing.

assembly (54, FO-12). Separator plate (53) separates

(3) Brake adjustment covers (24 and 40)

oil transfer plate (18, FO-13) and control valve body

permit access to the right and left brake adjustment

assembly (7, FO-12).

components.

b. Operation.

The oil transfer plates, in

(4) Left and right end covers (81, FO-7)

conjunction with the spacer plates, direct oil from and to

and (46, FO-8) support and enclose the output reduction

the proper passages in the valve bodies, converter

gears. They provide trunnion mounts which support the

housing and transmission top cover assembly.

rear end of the transmission. The right end cover

encloses the output driven oil pump.

Section II. OPERATION OF HYDRAULIC SYSTEM

position show only an approximate degree of movement

2-28.

Hydraulic Schematics

under certain conditions.

a. Full and Partial Schematics.

NOTE

(1) A schematic diagram of the entire

Variable conditions such as input

hydraulic system is illustrated in foldout 2 at the back of

this manual. This illustration may be unfolded for

speed, output speed, throttle opening,

reference during study in this section.

selector position, and viscosity of the

(2) Thirteen,

color-coded

partial

working fluid will affect the degree of

schematics are presented in this section to illustrate the

movement in certain valves.

various valves and hydraulic circuits involved in vehicle

(2) To link the hydraulic action with the

operation. Although every possible condition is not

corresponding mechanical action, references are made

illustrated, all operating conditions can be determined.

(when applicable) to Section III of this chapter which

This can be done by combining the desired

describes the mechanical functions in the power trains.

characteristics of one operating condition with those of

another.

Separate colors or color combinations--

2-29. Torque Converter or Lockup Drive

contained in the legend within the figure-indicate the

Regardless of the gear range or steer condition selected

circuits involved for the condition stated in the caption.

by the vehicle operator, drive from the engine to the

Areas not colored are inactive and contribute nothing to

range gearing either is through the torque converter

the hydraulic action. These areas indicate the circuits

(hydraulic) or lockup clutch (mechanical). Because the

usually filled with oil which is neither flowing nor

application of the lockup clutch is a function of turbine

pressurized.

speed, clutch engagement is illustrated for fourth-gear

b. Valve Positions.

conditions. The torque converter drive is illustrated

(1) In the partial schematics, the valves

for neutral, first, second, third, and reverse gears.

and other moving parts are shown in their proper

positions for the operating condition illustrated. Some

2-30.

System Pressure Pumps and Circuits.

valves will be at either one extreme position or the

(fig. 2-1)

other, while other valves will be shown at some

intermediate position.

Thus, those at intermediate

2-11