GMC 1982 Light Duty Truck Service Manual page 369

HUB REPLACEMENT
NOTICE: See N O T I C E on page 1 of this section,
regarding the fasteners in the following procedures for
Locking Hub Replacement.
AUTOM ATIC LOCKING HUBS
General Description (All Models)
The Automatic Locking Hub, shown in Fig. 3C-4K,
engages or disengages to lock the front axle shaft to the hub
of the front wheel. Engagement occurs whenever the vehicle
is operated in four-wheel drive. D isengagem ent occurs
whenever two-wheel drive has been selected and the vehicle
is moved rearward. Disengagement will not occur when the
vehicle is moved rearward if four-wheel drive is selected and
the hub has already been engaged.
The outer clutch housing is splined to the wheel. The
hub sleeve is splined to the front axle shaft. The clutch gear
is splined to the hub sleeve. The drag sleeve is keyed to the
wheel bearing retainer washer. Engagement occurs when
the clutch gear is moved on the splines of the hub sleeve to
engage the internal teeth of the outer clutch housing.
The cam surface of the steel inner cage forces the cam
follower and clutch gear to move outward toward the cover
and into engagement with the clutch teeth of the outer
clutch housing. A lug on the inside of the drag sleeve
retainer washer keys the washer to the spindle and two lock
nuts retain this washer in position on the spindle. Cutouts in
the drag sleeve engage the four tabs on the drag sleeve
retainer washer to hold the drag sleeve in a fixed position
with respect to the axle shaft. The one way clutch spring
(called a brake band) is positioned over the serrated portion
of the drag sleeve.
Engagement is accomplished (when four-wheel drive is
selected) by the movement of the axle shaft, causing one of
the tangs of the brake band to engage the steel outer cage
and hold the cage while the cam follower moves the clutch
gear into mesh with the outer clutch housing. One of the
tangs of the brake band is used for engagement. The other
tang is used to maintain free motion of the brake band
relative to the drag sleeve during four-wheel drive operation
(a fte r the hub lock
accomplished (after two-wheel drive has been selected) by
the reverse movement of the wheel causing the clutch gear,
hub sleeve, and cam follower to rotate. The cam follower
rotates away from the lugs of the plastic outer cage, allowing
th e follower to move to the disengaged condition. The
release spring then moves the clutch gear out of mesh with
the outer clutch housing to disengage the wheel from the
axle shaft.
Preliminary Checking
Before disassembling a unit for complaint of abnormal
noise, read the following:
• To obtain all-wheel drive, the transfer case lever must
be placed in (4L) or (4H ), at which time the hub locks
will automatically engage.
• To unlock (free wheel) the hubs, shift the transfer case
lever to (2H), then slowly reverse vehicle direction
approximately ten feet.
C O M PO N EN T REPLACEMENT
engages). Disengagem ent
• Incomplete shift from 2W D to 4W D, or disengagement
of only one hub lock may cause an abnormal sound
from the front axle. Shift to 4W D to stop the noise,
then unlock the hubs as described above.
Removal of Hub Lock Assembly
1. Remove the five screws ( i t e m # l , Fig. 3C-4K) which
retain the cover ( # 3 ) to the outer clutch housing
( # 10 ).
2. Remove the cover, seal ( # 4 ) , seal bridge ( # 1 1 ) , and
bearing components ( # 5 , 6, 7, 8).
3. Use needle-nose pliers to compress the wire retaining
ring ( # 9 ) , and pull the remaining components from
the wheel.
D IS A S S E M B L E L O C K IN G H U B C O M P O N E N T S
1. Remove the snap ring ( # 2 8 ) from the groove of the
hub sleeve ( # 1 8 ) .
2. T u rn the clutch gear ( # 1 7 ) until it drops into
engagement with the outer clutch housing ( # 1 0 ) . Lift
and cock the drag sleeve ( # 2 6 ) to unlock the tangs of
the brake band ( # 2 5 ) from the window of the inner
cage ( # 2 3 ) and remove drag sleeve and brake
assembly.
It is important that the brake band should never be
removed from the drag sleeve. The spring tension of the
brake band can be changed if the coils are over-
expanded and this could affect the operation of the hub.
3. Remove the snap ring ( # 2 4 ) from the groove in the
outer clutch housing.
4. Use a small screwdriver to pry the plastic outer cage
( # 2 2 ) free from the inner cage ( # 2 3 ) while the inner
cage is being removed.
5. Use a small screwdriver to pry the plastic outer cage
tabs free from the groove in the outer clutch housing.
Remove outer cage.
6. Remove the clutch sleeve ( # 1 8 )
components from the outer clutch housing.
7. Compress the return spring ( # 1 5 ) and hold the spring
in the compressed condition with fabricated clamps as
shown in Fig. 3C-5K. After the clamps are installed,
is
position the entire assembly in a bench vise so that the
vise holds both ends of the clutch sleeve. Remove the
retaining ring ( # 1 2 ) .
8. With the clutch sleeve assembly still in the vise, remove
the clamps holding the return spring. Slowly open the
vise to perm it releasing of the return spring in a
controlled manner. Remove the retainer seat, spring
and spring support washers ( # 1 3 , 14) from the hub
sleeve.
9. Remove the C-type retaining ring ( # 1 9 ) from the
clutch sleeve. It is necessary to position the sleeve
assembly so that the C-ring ends are aligned with the
legs of the cam follower, allowing removal between the
two legs.
10. Remove the conical spring ( # 2 0 ) from between the
cam follower and the clutch gear.
11. Separate the cam follower ( # 2 1 ) from the clutch gear
( # 1 7 ) .
FRONT SUSPENSION 3 C -2 7
and atta c h e d