Chapter 12. STEERING SYSTEM MAINTENANCE

TM 10-3930-673-34

CHAPTER 12

STEERING SYSTEM MAINTENANCE

Para

Contents

Page

Section III. Description and Data

12-1.

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1

12-2.

Principles of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1

Section IV. Steering System Maintenance Procedures

12-3.

Drive Wheel Spindle Replacement/Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12-3

12-4.

Emergency Steering Pump Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12-9

12-5.

Steering Control Valve Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12-10

12-6.

Tie Rod Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Section III. DESCRIPTION AND DATA

12-1. GENERAL

This chapter covers maintenance procedures for the steering system components, as well as principles of

operation.

12-2. PRINCIPLES OF OPERATION

a. System Components. The steering system components include steering valve (1), steer select valve (2),

and four steering hydraulic cylinders (3). Additional, related components include the large (3.94 cu. in.)

section of dual gear pump (4) and priority valve (5). Making up the emergency steering system are an electric

motor driven pump (6) and pressure switch (7). Pressure switch (7) senses hydraulic pressure in the main

steering circuit and closes to turn on the emergency steering pump motor and a warning light in the cab when

main system pressure drops to below approximately 75 psi (517.13 kPa).

b. Normal System Operation. Hydraulic flow from the large section of dual gear pump (4) is directed to

the inlet port of priority valve (5). The function of priority valve (5) is to ensure that sufficient oil flow goes to

steering valve (1) to permit normal steering in the event that any attachment functions are being operated at

the same time that steering is occurring. The priority valve (5) will deprive the attachment functions of oil

flow in order to maintain adequate flow for steering. Component overpressure protection is provided by relief

valve (8) which is built into priority valve (5).

As long as the steering wheel is not being turned, sleeve and spool assembly (9) remains centered and

gerotor (10) remains stationary. Priority valve (5) will then direct pump flow to the main control valve. The

pressure resulting from the blocking condition of the centered steering valve sleeve and spool assembly (9)

keeps priority valve (5) shifted to the right (as shown) to permit flow to the main valve. The steering

cylinders (3) are held stationary by trapped oil in the lines.

Turning the steering wheel in either direction will cause the spool in sleeve and spool assembly (9) to rotate

with respect to the sleeve. As this happens, oil is allowed to flow through passages in sleeve and spool

assembly (9) to gerotor (10). This oil flow causes the gear in gerotor (10) to rotate, directing flow back to sleeve

and spool assembly (9). The redirected flow now exits sleeve and spool assembly (9) via the proper work port

12-1