GMC 4000 Series Service Manual page 483

Sec. 9A
Page 472
MECHANICAL STEERING
S P R IN G S C A L E
rigure 4 — Checking Steering W heel Rim Pull
CHECKING WORM BEARING ADJUSTMENT
1. Disconnect drag link or connecting rod from
Pitman arm. Note relative position of linkage and
Pitman arm so parts may be reassembled in same
relative position. Refer to "Steering Linkage" later
in this section for correct procedures.
2. Loosen lock nut and turn lash adjuster (fig.
3) a few turns counterclockwise to relieve load
from worm bearings and to provide clearance be­
tween the sector gear and worm ball nut.
3. Turn steering wheel GENTLY in one direc­
tion until stopped by gear "stops" or by reaching
end of travel, then back away one full turn.
CAUTION: DO
wheel hard against "stops" when linkage
is disconnected from Pitman arm as dam­
age to ball guides may result.
4. Attach spring scale (J -544-01) at rim of
wheel as shown in figure 4. Pull on scale in a line
at right angle to wheel spoke and measure the
amount of pull required to keep the wheel moving.
If worm bearings are properly adjusted, reading
on spring scale should be between 1% and2 pounds.
If pull is not within 1% to 2 pounds, worm bear­
ings require adjustment. If "rough" or "lumpy"
action is noted during check, worm bearings are
probably damaged. Steering gear should then be
removed, disassembled, and bearings examined.
If worm bearings do not require adjustment, adjust
Pitman shaft lash as described later in this section.
Adjust worm bearings as follows:
WORM BEARING ADJUSTMENT
1. Loosen adjuster lock nut (22) (fig. 1) at
shaft end of steering gear and turn worm bearing
adjuster screw (23) clockwise until there is no per­
G M C S E R V I C E M A N U A L
NOT turn steering
ceptible end play in the worm.
2. Using spring scale (J-544-01), checksteer-
ing wheel rim pull as outlined previously. Turn
adjuster screw until a pull of 1% to 2 pounds is
obtained on spring scale at steering wheel.
3. Tighten adjuster lock nut to torque recom­
mended in "Specifications."
PITMAN SHAFT LASH ADJUSTMENT
1. Center steering gear by turning steering
wheel from extreme right to extreme left positions,
counting the exact number of turns. Turn wheel
back exactly half-way, to center position. Mark
wheel at top or bottom center with a piece of tape.
2. Loosen lash adjuster lock nut and turn ad­
juster screw (fig. 3) clockwise to remove all back
lash between gear teeth. Tighten lock nut to 25-35
foot-pounds torque, then check steering wheel rim
pull as outlined previously. Measure greatest pull
as wheel is pulled through center position. Rim
pull should be 2% to 3% pounds.
3. If rim pull is not within specified lim its,
loosen lock nut and turn lash adjuster to obtain
proper wheel rim pull.
IMPORTANT: Always check wheel rim pull
after lock nut has been tightened.
4. On vehicles equipped with the 553-D-17
type steering gear, turn back-up adjuster in until
it bottoms, then back off 1/8 to 1/4 turn and tighten
lock nut to torque listed in "Specifications" at end
of this section.
5. After all adjustments have been completed,
reconnect drag link or connecting rod to Pitman
arm as described under "Steering Linkage" later
in this section.
STEERING GEAR REPLACEMENT
(Refer to Figures 5 and 6)
If the steering gear cannot be properly adjust­
ed, or if during adjustment procedures "rough"
operation is noticed, the steering gear must be re­
moved from the vehicle and overhauled. The steer­
ing gear must be removed from the vehicle for all
overhaul or repair procedures.
STEERING GEAR REMOVAL
1. Disconnect steering linkage from Pitman
arm.
2. Scribe an alignment mark on steering gear
worm shaft and clamp yoke or coupling on steering
gear lower or intermediate shaft (fig. 6).
3. Remove bolt attaching lower or intermed­
iate shaft clamp yoke or coupling to steering gear
worm shaft (3).
NOTE: When removing flexible coupling-type
joint (fig. 6), remove the two bolts and nuts which
secure lower clamp plate to balance of rag joint
assembly.