GMC 4000 Series Service Manual page 137

Sec. 4A
Page 130
REAR AXLE A N D CONTROLS
line connections with hydraulic brake fluid. If leak
exists, fluid will be drawn into connection with en­
gine idling and control lever in "LOCK" position.
4. Remove line having leaking connection.
Slide tube nut back on tube and remove all particles
of seal ring from tube and from inside of nut. Slip
new seal ring over tube end. Insert tube into fitting
and seat solidly. Slide seal ring (do not roll) into
fitting (fig. 7). Thread tube nut into fitting and
tighten slowly and firm ly.
5. Repeat above test on opposite vacuum line,
SYMPTOM
NOISE ON DRIVE
E xcessive Pinion Gear B a c k la sh .................
Worn Pinion and Bevel G e a r .......................
Worn Pinion B earings ......................................
Loose Pinion Bearings ..................................
E xcessive Pinion End P l a y .............................
Worn Differential Bearings
Loose Differential B e a r in g s ..........................
Excessive Bevel Gear R u n -O u t.................
Low Lubricant Level ...............................
Wrong or Poor Grade L u b r ic a n t...............
Bent Axle Housing ............... Straighten or Replace
NOISY ON COAST
Axle noises heard on drive will
usually be heard also on coasting;
although not as loud ............
Pinion and bevel gear too tight (audible when
decelerating & disappears when driving) . Adjust
INTERMITTENT NOISE
Warped Bevel G e a r ........................................
Loose Differential Case B o lt s ....................
AXLE REPLACEMENT
REMOVAL
1. Jack up rear of vehicle until load is re­
moved from springs, then place blocks under
frame to prevent accidental dropping of vehicle.
2. Disconnect hydraulic or air brake lines,
whichever is used. Refer to BRAKES (SEC. 5).
3. Disconnect electric wiring or line from
shift chamber if vehicle is equipped with a 2-speed
axle.
4. Disconnect propeller shafts as directed in
"PROPELLER SHAFTS" (SEC. 4D).
5. Disconnect torque or radius rods, if used,
as directed in "REAR SPRINGS" (SEC. 4B).
G M C S E R V I C E M A N U A L
REAR AXLE SERVICE DIAGNOSIS
PROBABLE
REMEDY
Adjust
Replace
R ep lace
Adjust
Adjust
....................... Replace
Adjust
Replace
Replenish
Replace
Adjust or Replace
Replace
Tighten
REPLACEMENT A N D OVERHAUL
being sure to change shift button.
6. If vacuum drop is still excessive after all
connections have been checked, leakage in one of
the units is indicated. Remove each unit and over­
haul or replace as required.
AIR CLEANER
Air cleaner removes dirt particles from at­
mosphere which passes into the control valve and
other units. Air cleaner should be removed and
cleaned at regular intervals.
SYMPTOM
CONSTANT NOISE
Flat Spot on Pinion
or Bevel Gear Teeth ...............................
F lat Spot on B e a r i n g s ......................................
Worn Pinion S p lin e s .....................................
Worn Axle Shaft Dowel H o le s ....................
Worn Hub Studs ...........................................
Bent Axle Shaft .............................................
NOISY ON TURNS
Worn Differential Side Gears
and Pinions ................................................
Worn Differential S p id e r .............................
Worn Differential Thrust Washers . . . .
Worn Axle Shaft Splines .............................
FAILS TO SHIFT
INTO HIGH OR LOW
Defective Electrical Circuit
Defective Shift Unit .....................................
Lack of Air P r e s s u r e ..................................
Low V acuum ...................................................
6. Disconnect spring U-bolts as directed in
"REAR SPRINGS" (SEC. 4B).
7. Roll axle out from under vehicle, then re­
move wheels, hubs, and bearings as directed in
"REAR HUBS AND BEARINGS" (SEC. 4C).
8. Whenever another axle is to be installed
instead of the one removed, it may be necessary to
remove two speed shift unit, and brake chambers.
Refer to respective sub-sections for instructions.
INSTALLATION
1. If brake chambers or two-speed shift unit
has been removed, they should be reinstalled as
directed in respective sections.
2. Install hubs, wheels and tires as directed
PROBABLE
REMEDY
Replace
R ep lace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
.................... Correct
Replace
Correct
Correct