GMC 1982 Light Duty Truck Service Manual page 495

CASE HALF — L.H
SHIM
LATCHING
ASSEMBLY
4. Start engine making sure that carburetor is set to
provide a low idle speed of 600-800 rpm.
5. Place transmission in drive range and apply brakes.
With manual transmission, depress clutch and place
transmission in first gear.
6. Lock one rear wheel by pulling one parking brake cable
from under the vehicle.
7. With engine at low idle, slowly release brakes. With
manual transmission, slowly engage clutch.
8. Locked rear wheel will remain stationary and free
wheel will begin turning. It is important that brakes or
clutch be released slowly enough to start the free wheel
turning and allow the free wheel to gradually increase
in speed. As speed of the free wheel is increased, the
differential will lock causing the rotating wheel to stop
or both wheels to turn at the same speed. The engine
may stall if equipped with a manual transmission. It
may be necessary to
approxim ately 10 mph (16 km /h) is indicated on
vehicle speedometer to cause differential lock. If
GUIDE CLIP (6)
EARED
^ \ DISC (3)
SPLINED DISC (2)
BRACKET
Fig. 4B6-2H--3/4 Ton Unit
accelerate engine until
GUIDE CLIP (6)
DISC
PACK S/A
CASE
H A L F — R .H
GOVERNOR
ASSEMBLY
SIDE GEAR
THRUST BLOCK (2)
indicated speed can be increased beyond 20 mph (32
km /h) without causing differential lock, the unit is not
functioning properly.
Rapid release of brakes or clutch, or rapid acceleration
of engine wil invalidate test.
9. Lock opposite rear wheel and repeat procedure. The
following chart provides guidelines for diagnosis and
repair of differential complaints.
UNIT REPAIR
Due to critical
differential side gears and case cannot be serviced
separately. If any side gear or case damage is found the
entire differential must be replaced.
Internal clearances are such that shims, reaction block
and thrust rings should not be replaced unnecessarily even if
slight wear indications are present. If shims, reaction block,
or thrust ring must be replaced due to damage, correct
measurement and
followed. Failure to do so may disturb critical clearances
and could result in differential complaints.
REAR AXLE
SCREW (3)
SHIM
v
\
THRUST
WASHER (3)
PINION
'GEAR (3)
PINION YOKE
internal clearance dimensions,
replacement procedures must be
4B6-13