Chevrolet 70 1969 Series, Shop Manual

Page: 144 / 913

REAR SUSPENSION 4A-5
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 connector fitting and seat
tube solidly in fitting (fig. 6). Slide seal ring (do
not roll) into fitting. Thread tube nut into fitting
and tighten slowly and firmly.
4. Coat entire surface of control valve and
check valve with soap suds to check for leakage.
Control valve may have some leakage past plunger.
Liberally coat control lever slot in control valve
body (with dial plate removed). Leakage should not
exceed 1-inch soap bubble in one second. Leakage
at control valve inlet and outlet connections is not
permissible. If leakage is evident in any of the
other units, faulty unit should be replaced.
V A C U U M L E A K A G E T E S T S
1. Temporarily install a " T " fitting at shift
chamber and connect a vacuum gauge between
chamber and vacuum line. Tighten gauge connec­
tions firmly.
2. Start engine and place differential lock
control lever in " L O C K " position. Run engine
long enough to obtain maximum vacuum, then stop
engine and note rate of vacuum drop. If drop ex­
ceeds 1 inch in 15 seconds, leakage is excessive.
3. If leakage is indicated, coat all vacuum
line connections with hydraulic brake fluid. If leak
Figure 6 — Tubing Connection Seal
exists, fluid will be drawn into connection with en­
gine idling and control lever in " L O C K " 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. 6). Thread tube nut into fitting and
tighten slowly and firmly.
5. Repeat leakage test as directed in steps 1
and 2. If vacuum drop is still excessive, leakage
is in one of the shift control units. Remove each
unit and overhaul or replace as directed later
under individual headings.
REAR AXLE SERVICE DIAGNOSIS
PROBABLE PROBABLE
S Y M P T O M R E M E D Y S Y M P T O M R E M E D Y
N OISE O N D R IV E
Excessive Pinion to Bevel Gear Backlash . Adjust
Worn Pinion and Bevel Gear .................. Replace
Worn Pinion B earings............................... Replace
Loose Pinion Bearings ............................... Adjust
Excessive Pinion End Play
....................... Adjust
Worn Differential Bearings .................. Replace
Loose Differential Bearings .................. .. Adjust
Excessive Bevel Gear Run-Out............... Replace
Low Lubricant L e v e l ............................ Replenish
Wrong or Poor Grade Lubricant............. Replace
Bent Axle Housing .............Straighten or Replace
N O ISY O N C O A S T
Axle noises heard on drive will
usually be heard also on coasting;
although not as loud .......... Adjust or Replace
Pinion and bevel gear too tight (audible when
decelerating and disappears when driving)Adjust
IN T E R M IT T E N T NOISE
Warped Bevel Gear ................................. Replace
Loose Differential Case Bolts ............... Tighten
C O N S T A N T NOISE
Flat Spot on Pinion or Bevel Gear Teeth . Replace
Flat Spot on Bearings ..................... .. Replace
W orn Pinion Sp lin es.................. ............... Replace
Worn Axle Shaft Dowel H o l e s .................. Replace
Worn Hub Studs......................................... Replace
Bent Axle Shaft ......................................... Replace
N O ISY O N T U R N S
Worn Differential Side Gears & Pinions . Replace
Worn Differential Spider.......................... Replace
W orn Differential Thrust Washers . . . . Replace
Worn Axle Shaft S p lin e s .......................... Replace
FAILS T O SHIFT
IN T O HIGH O R L O W
Defective Electrical Circuit .................. Correct
Defective Shift U n i t ................................. Replace
Lack of Air Pressure ............................ Correct
Low Vacuum ........................................... Correct
CHEVROLET SERIES 70-80 H EAVY DUTY TRUCK SH O P M A N U A L