Section III. TORQUE PATHS THROUGH TRANSMISSION

TM 9-2520-249-34&P

during steer) to flood the clutch disks and prevents

a. Composite Illustration. Figure 2-13 is a

excessive heat buildup during partial application. When

composite of all driving conditions which can occur in

the apply piston returns to its seat, the check valve

the output sections of the transmission. The conditions,

closes.

as illustrated, can occur either independently or

c. Brake and Steer Coolant Pressure

simultaneously. The clutch apply circuits are color

Retaining Valve. The spring-loaded retaining valve

coded to match the charging circuits shown in figures 2-

2 through figure 2-12. The lubrication, brake coolant,

opens when the pressure in the coolant circuit is not

and air circuit are color coded and match the circuits in

escaping through the steer coolant check valve. In the

figure 2-1 through figure 2-12.

open position, the pressure-retaining valve allows

b. Steer Coolant Check Value. The check

coolant to flood the clutches and brake disks. The valve

closes when pressure in the coolant circuit is reduced.

valve opens when the reverse piston travels to engage

the reverse clutch. This allows coolant (present

Section III. TORQUE PATHS THROUGH TRANSMISSION

illustrations (normal and pivot) are shown with the

2-46.

Definition of Torque Path

clutches in the full-apply condition. Lesser applications

a. A torque path is the route by which engine

of the clutches will lengthen the radius in which the

torque is directed through the transmission from

vehicle travels.

transmission input to output. Each torque path is

2-48. Torque Transmitted

established by the application of a combination of

Torque Converter and Lockup Clutch.

clutches. Each travel condition (forward or reverse) and

(1) In every range, and in neutral, torque

each steer condition (forward or reverse) requires the

from the engine must be transmitted to the converter

application of a different combination of clutches.

output shaft either hydraulically or mechanically. At

b. Changes in the torque paths as a result of

lower speeds (until sufficient pitot pressure is produced),

torque converter or lockup operation is not important to

the drive is hydraulic.

the basic torque paths. Any given torque path can vary

(2) At higher speeds (lockup clutch

in this respect. Neutral condition is illustrated as a

engaged) the drive is mechanical. Although either type

torque path, but is not considered as being a complete

of operation is possible in neutral and all ranges,

torque path.

converter operation is illustrated in neutral, first gear,

2-47. Torque Path Illustrations

second gear, third gear and reverse. Lockup operation

a. A series of cutaway illustrations (fig. 2-14

is illustrated only in fourth gear.

through fig. 2-32 are color coded to show the function of

b. Output Reduction Gears. In every gear

each component involved in the torque path. The

during straight travel or steer, torque is transmitted from

torque paths for all possible situations are not shown

the output shaft to the vehicle by two spur gears

because the explanation of steer toward one direction

(transfer drive and transfer driven) at each side of the

serves to explain the opposite steer, and because

transmission. The speed reduction ratio is 2.222 to 1.

converter to lockup operation can be employed, as

desired, in the power flows.

b. The principal paths shown in the

illustrations are neutral, straight travel in each range,

normal steer to either left or right in all ranges, and pivot

steer to either left or right in all ranges. The steer

2-29