Steering Gear Assembly - TM-10-3930-242-340171

TM 10-3930-242-34

piston and no circulation of oil in the lines to the

c y l i n d e r ; however, oil is circulating from the

p u m p through the control valve to the reservoir

w i t h sufficient pressure only to overcome fric-

tion of lines and fittings,

( 4 ) Whenever the operator's efforts at the

s t e e r i n g wheel overcome the centering effect of

t h e springs and/or hydraulic reaction, the valve

s p o o l is moved axially, restricting one of the

r e t u r n passages to the outlet port, thus causing

an immediate increase in pressure at one of the

cylinder ports and in one end of the cylinder. At

t h e same time, the other return passage is en-

l a r g e d , allowing the oil from the discharging

e n d of the cylinder free passage to the outlet

p o r t and return to the reservoir. The immediate

e f f e c t is increased pressure in one end of the

cylinder to actuate the piston which applies

h y d r a u l i c power directly to the steering gear

p i t m a n arm or linkage part to which the cylin-

der is attached. Full pressure is obtained with a

s p o o l travel of about sixty-five one-thousandths

o f an inch. The slightest movement results in a

p r e s s u r e differential.

b. Removal.

(1) Remove the horn button steering wheel

by gripping with a downward pressure and

turning counterclockwise.

( 2 ) Use a suitable puller and remove the

steering wheel (TM 10-3930-242-12).

( 3 ) Use a suitable puller and remove the

Figure 5-16. Steering mode selector valve, removal and in-

s t e e r i n g wheel arm from the pitman arm.

stallation.

(4) Tag and disconnect hydraulic lines as

necessary. Place dust caps over openings to pre-

( 2 ) Power steering control valves generally

v e n t foreign matter from entering the hydraulic

u t i l i z e the hydraulic pressure in the steering

system.

s y s t e m to urge the valve spool to its neutral

(5) Remove column from upper support

p o s i t i o n . This is called hydraulic reaction. As

bracket.

the pressure in the hydraulic cylinder builds up,

( 6 ) Remove mounting flange bolts and re-

t h e hydraulic centering force increases. Thus,

m o v e gear from chassis.

t h e operator's effort on the steering wheel in

c. Disassembly. Refer to figure 5-18 and dis-

t u r n i n g a corner is greater than in a straight

a s s e m b l e the steering gear assembly.

a h e a d road correction condition. Because the

d. Cleaning and I n s p e c t i o n .

h y d r a u l i c pressure is low in the straight ahead

( 1 ) Clean all parts thoroughly, using clean

driving conditions, it is necessary to add center-

s o l v e n t P-D-680, or equal.

i n g springs to assist the hydraulic reaction in

( 2 ) Inspect the components for wear, burrs,

giving the system road feel. The feel and steer-

s c o r e d areas and other damage.

i n g effort created by the centering springs is

( 3 ) Replace all defective parts,

c o n s t a n t for any steering condition and is gen-

e. Reassemble. Refer to figure 5-18 and reas-

erally tailored to suit the vehicle application by

s e m b l e the steering gear assembly.

c h a n g i n g the spring load to give the degree of

f. Installation. Install the steering gear as-

s t e e r i n g effort desired.

s e m b l y in the reverse order of removal.

g. Thrust Bearing Ajustment Procedure.

(3) When the valve is in the center position,

(1) Remove capscrews (39, fig. 5-18) holding

the oil pressure at its two cylinder ports is low

u p p e r cover (37) and remove cover and jacket

and equal and produces ineffective forces in the

tube assembly (40).

c y l i n d e r . This results in no movement of the

5-33