GMC 4000 Series Service Manual page 502

at rear of this section. It is intended as a quick
reference and covers most problems encountered.
POWER STEERING GEAR
REPLACEMENT
REMOVAL
1. Mark steering gear worm shaft and coup­
ling or clamp yoke on steering shaft to assure
installation in the same position.
2. Remove cotter pin and nut, attaching drag
link or connecting rod to Pitman arm. Use a soft
hammer to tap drag link or connecting rod loose
from Pitman arm.
3. Remove Pitman arm to shaft nut and wash­
er, then use puller (J-3186) to remove Pitman arm
from shaft.
4. Drain as much fluid as possible from the
steering gear.
5. Disconnect control valve to pump return
tube, pump to control valve pressure tube, and
control valve to power cylinder right- and left-
turn tubes from control valve ports.
IMPORTANT: Cover or plug exposed tubes and
ports to prevent dirt from entering the hydraulic
system .
6. Remove steering shaft to steering gear
worm shaft clamp bolt and nut.
7. Remove bolts, nuts, and washers which at-
TROUBLESHOOTING THE
NOISE
Several different types of noise may be heard
with the control valve steering gear. Troubleshoot
noises as follows:
RATTLE OR CHUCKLE
1. Cause could be loose adjustment. Adjust
thrust bearing preload.
2. Noise could be caused by steering gear
being loose on frame.
a. Check steering gear installation as des­
cribed previously in this section under "Steering
Gear Replacement."
b. Torque steering gear mounting bolts to
torque specified under "Specifications" later in
this section.
3. Coupling pin stops hitting against the upper
flange could also cause this type of noise. Re-align­
ment of the shaft with the gear or an endwise ad­
justment of shaft should correct this condition.
NOTE: A slight rattle may occur on turns be­
cause of the increased lash off the high point. This
is normal.
HISS
There is some noise in all power steering
G M C S E R V I C E M A N U A L
tach steering gear assembly to frame left side
member. Remove steering gear and control valve
from frame, and steering shaft.
INSTALLATION
tion with mark on worm shaft located as described
in "Specifications" at end of this section.
ber and at same time, slide worm shaft into steer­
ing shaft clamp yoke or coupling. Check to make
sure alignment marks are aligned.
steering gear to frame side member. Tighten bolts
to torque listed in "Specifications."
ing the blank serrations. Install washer and nut on
shaft and tighten to 185 to 215 foot-pounds torque.
man arm and attach with nut. Tighten nut to 125 to
150 foot-pounds torque, advance to next slot and
install cotter pin.
pump to control valve pressure tube, and right-
and left-turn tubes from power cylinder to control
valve ports. Tighten fittings to torque listed.
er level as described under "Bleeding Hydraulic
System" previously.
POWER STEERING GEAR
gears which cannot be eliminated. One of the most
common is the "hissing" sound most evident at
standstill parking with wheels at end of travel. The
"hissing" noise is usually caused by a faulty valve.
extremely objectionable, since the replacement
valve will also have a slight "hissing" noise. Be
sure, however, that the steering shaft and gear
are properly aligned as the shaft rotates, since
misalignment will transmit the "hissing" noise
into the cab.
VALVE SQUAWK
ing from a turn may be caused by a worn dampener
ring on the valve spool or by a loose or worn valve
body. In both cases replace faulty parts.
INTERNAL LEAKS
increase in the steering effort when turning the
wheel fast. If this situation should occur, replace
the control valve.
POWER STEERING
1. Adjust steering gear to straight ahead posi­
2. Position steering gear on frame side mem­
3. Install bolts, nuts, and washers to attach
4. Position Pitman arm on Pitman shaft, align­
5. Connect drag link or connecting rod to Pit­
6. Connect control valve to pump return tube,
7. Bleed the system and fill reservoir to prop­
Do not replace the valve unless the "hiss" is
Valve squawk when turning or when recover­
STEERING GEAR LEAKS
High internal leakage will cause a momentary
Sec. 9B
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