Chevrolet 70 1969 Series Shop Manual page 142

C A U T IO N : USE D IF F E R E N T I A L L O C K O N L Y
W H E N N E C E S S A R Y A N D N O T
DR IVIN G .
Air operated differential lock utilizes air
pressure from the air brake system for its oper­
ation. Units used in air-operated power shift sys­
tem are: Control Lever, located on instrument
panel in cab; Shift Control Valve, mounted on en­
gine side of dash; Check Valve, installed in air
line at control valve air inlet; Differential Lock
Shift Cylinder or Chamber, mounted on forward
rear axle, and interconnecting air lines andfittings.
OPERATION
When the control valve lever (fig. 4) is moved
to " L O C K " position (or "Push-Pull" knob is pulled
outward) the exhaust port in control valve is closed
and air inlet valve is opened. Air pressure is then
admitted through air lines to unit on forward rear
axle.
Moving the control valve lever (fig. 4) to " U N ­
L O C K E D " position (or "Push-Pull" knob is pushed
inward) closes air inlet valve and opens shift unit
to pass back through air lines and exhaust to at-
At regular intervals, the following lubrication,
inspection, and maintenance procedures should be
accomplished and corrective
wherever necessary.
LU B R IC A T ION
Lubrication intervals, method of filling and
draining, also type of lubricant and capacities for
all axles are covered in LU B R IC A T IO N (SEC. 0).
Examine housing cover, pinion oil seal re­
tainers, and axle shaft flanges for lubricant leaks.
Tighten bolts or nuts, or replace gaskets and seals
as necessary to correct leaks.
M O U N T IN G
Check for axle misalignment. Select a point at
one side of vehicle and a corresponding point at
opposite side. Measure distances between points
selected and identical points at each end of axle
assembly. If distances are not equal, axle misalign­
ment is indicated and rear spring should be checked
for correct installation.
Refer to R E A R SPRINGS (SEC. 4B) for spring
U-bolt tightening instructions, also for torque rod
inspection and maintenance.
A X L E S H A F T F L A N G E M O U N T IN G
Axle shaft flanges are retained to hubs with
stud nuts and dowels on all axles.
F O R G E N E R A L
MAINTENANCE O N VEHICLE
measures taken
f
I N T E R
D I F F E R E N T I A L
L O C K
Figure 4 — Inter-Axle Differential Lock Control Lever and Plate
mosphere through the control valve on dash. Shift
return compression spring returns sliding clutch
gear to " U N L O C K E D " position.
Check valve in air supply line located behind
control valve, prevents loss of air pressure in air
shift axle control system if air supply pressure
should drop while control valve is in " L O C K "
position.
1. Check tightness of stud nuts at regular in­
tervals. Tighten 1 /2 " nuts to 30-40 ft.-lbs. torque,
or 5 /8 " nuts to 50-60 ft.-lbs. torque.
2. The studs must be straight and dowels of
correct taper must be used. There should always
be a slight clearance between nuts and driving
flange when nuts are drawn up (fig. 5). No clearance
at this point indicates excessive wear at studs,
dowels, or holes in flange. Replacement of worn
parts is the only remedy.
3. If stud nuts are not tightened to torque
specified, play between flange and studs will cause
bent or broken studs, also worn tapered holes in
flange of axle shaft.
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SH OP M A N U A L
REAR SUSPENSION 4A-3
A X L E \
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. _ _. U N L O C K \
TPM-3224