STEERING AXLE ASSEMBLY

TM 10-3930-623-34

direct hydraulic pressure as required for either right or

1-27. Additional oil from the pump is used by the control

left turn assist. The spool is attached to the valve body

valve to provide forward or reverse directional control to

at one end, and through a torsion bar to the steering

the vehicle. The control valve includes a pressure

gear stub shaft at the other end. Turning the steering

regulator valve, a brake pedal operated inching valve, a

wheel will steer the wheels without power assistance,

forward and reverse clutch supply valve, and a forward

through the torsion bar, spool and valve body, until more

and reverse selector valve, with neutral position. These

than about three pounds pull at the rim of the steering

four valves are essentially in series in the control circuit.

wheel is required. At this amount of resistance the

Regulated pump pressure is delivered to the inching

torsion bar twists, shifting the spool in the valve body, to

valve, which can either deliver it through, or partially or

valve hydraulic fluid as required to supplement steering

completely shut off this pressure as the operator

effort in the direction in which the wheel is turned, as

requires, for inching operations while maintaining high

diagramed in figure 1-6. Note that the rack-piston nut is

engine speed for hoisting. Pressure on the brake pedal

geared directly to the pitman shaft. Power assistance is

controls the degree of clutch slippage for inching, while

proportional to demand, and ceases when reduction in

the position of the selector valve determines which

torsional load permits the torsion bar to return the valve

clutch will be engaged.

spool to neutral. Hydraulic power is taken from the truck

main hydraulic pump via a pressure reducing priority

1-28. DRIVE AXLE (See figure 1-9). This assembly is

valve on the main hydraulic pump, connected by tubing

a double-reduction drive axle, bolted directly to the front

directly to the steering gear housing.

of the transmission. The output shaft of the transmission

includes the drive pinion gear which mates with the ring

gear of the differential assembly to provide the first

1-22. STEERING AXLE ASSEMBLY (See figure 1-5).

The steering axle assembly is mounted on two neoprene

reduction. Internal gears at the outer end of the first

blocks located to permit a degree of movement to the

drive axles drive sun gears to give the second stage

axle necessary to pass over irregular surfaces. The

reduction to the final drive axles and the wheels.

steering axle layout, and its relationship to the power

steering system is shown in figure 1-5.

1-29. The hydraulic brake assemblies at each wheel are

pedal actuated as service brakes and handle operated

1-23. Two equal length tie rods connect a center-

by mechanical linkage as parking brakes.

A self-

mounted bellcrank to each of the steering knuckles.

adjusting feature eliminates periodic adjustment to

Steering axle king pins are mounted in true vertical

compensate for lining wear. The brake master cylinder

position to provide similar steering characteristics in

is a conventional automotive type, connected to a wheel

either forward or reverse travel. The pneumatic tired

cylinder at each front wheel by hydraulic lines. The

wheels of the steering axle are not fitted with brakes.

service brake shoes serve also as parking brakes, being

actuated by linkage from the hand brake lever next to

1-24. TRANSMISSION (See figures 1-7 and 1-8). The

the operator's seat. The operator can adjust any slack

transmission is a power-shifted single ratio forward and

from the parking brake linkage by turning a knurled knob

reverse unit. A torque converter transmits engine output

at the top of the parking brake lever.

to the transmission input shaft. The transmission is

mounted directly to the engine and drive axle. No

1-30. UPRIGHT CARRIAGE AND FORK ASSEMBLY.

intervening drive shaft is used. Shifting between forward

The upright carriage and fork

(See figure 1-10).

and reverse is accomplished by engagement of either a

assembly consists of four main items which are

forward or reverse wet clutch in the unit. These clutches

described in the following paragraphs.

are engaged by hydraulic pressure selected by a control

valve.

1-31. OUTER UPRIGHT. This item is a welded one-

piece assembly attached to the frame of the vehicle. It

1-25. The clutches are contained in one large balanced

encloses the hydraulic hoist cylinder and inner upright

drum assembly, and the plates drive concentric shafts.

assembly. The outer upright is pivot mounted on the

The outer shaft has a gear mounted on it which is in

frame to permit tilting by the tilt cylinder of the entire

direct mesh with the output gear on the output shaft.

carriage and fork assembly as necessary.

This transmits forward rotation to the output shaft. A

gear on the inner shaft drives the output shaft through an

1-32. INNER UPRIGHT. This item is a one-piece

idler gear to give reverse drive. The main case is of two

welded assembly mounted within the outer upright. The

piece construction and the rear half contains a heavy

hydraulic hoist cylinder, mounted in the base of the outer

diaphragm midwall which forms one side of a straddle

upright, is attached at the top to the inner upright

mounting for the output gear and shaft. Oil passages

crossmember.

The inner upright is raised by the

are internal except for the lines to the transmission oil

hydraulic cylinder.

cooler.

The oil supply is common for the torque

converter, transmission, and drive axle, including the

The crosshead

1-33.

CROSSHEAD ASSEMBLY.

drive wheel bearings.

assembly is mounted on the top end of the hoist cylinder

primary plunger. Chains, secured at one end to the hoist

1-26. An internal gear pump driven by the torque

primary. cylinder, pass over rollers on the crosshead

converter hub supplies oil to the torque converter

assembly and are secured to the lift carriage assembly.

through a metering orifice and to a control valve

Raising the hoist cylinder primary plunger raises the

assembly in the transmission housing. Oil delivered to

crosshead assembly to hoist the lift carriage and forks by

the torque converter maintains circulation through the

the chain

converter to the oil cooler, or heat exchanger in the

engine radiator.

1-6