Chevrolet 70 1969 Series, Shop Manual

Page: 566 / 913

REAR AXLE 4-11
after the pinion has been properly set. W ith red lead
m ethod, backlash is obtained first, then proper tooth con­
tact is established.
W O R N G E A R BA CKLA SH
Gears that have been in service for extensive periods,
form running contacts due to wear of teeth; therefore, the
original shim pack (between pinion cage and carrier)
should be m aintained when checking backlash. In the
event backlash exceeds m axim um tolerance, reduce back­
lash only in the am ount that will avoid overlap of worn
tooth section. Sm oothness and roughness can be noted by
rotating bevel gear.
If a slignt overlap, as illustrated in Figure 18, takes
place at worn tooth section, rotation will be rough.
If new gears are installed, check backlash with dial in­
dicator. Figure 19 illustrates typical m ethod of checking
backlash with dial indicator.
Backlash is increased by moving bevel gear away from
pinion, and m ay be decreased by moving bevel gear
tow ard pinion.
Backlash is accom plished by threaded differential bear­
ing adjusters. Keep in m ind th at when one adjuster is
tightened, the opposite adjuster m ust be loosened an equal
am ount to m aintain previously established bearing adjust­
ment.
P IN IO N SETTIN G PROCEDURES
The pinion setting gauge (J-5341) is a direct reading
m icrom eter m ounted in arbor. A d apter discs, which fit in
differential bores are m ounted in sleeves that fit over the
arbor. Different ad apter discs are required for various
axle models as listed in S P E C IA L T O O L S section of this
publication. T he proper adapter discs hold the gauge as­
sembly so that centerline of arbor coincides with center-
line of carrier bores.
TERMS USED
There are several teim s used in following text to des-
Figure 18— Worn Tooth Cross Section
cribe the various dim ensions which m ust be determ ined
when using the pinion gauge setting method. These are:
1. N O M IN A L A S S E M B L Y D IM E N S IO N . This di­
mension, which varies on different model axles, is ac-
Figure 19 — C h e c k in g G e a r B a c k la sh w ith D ia l In d icator
tually the distance between the centerline of the drive
gear (or differential carrier bore) and the end of the
drive pinion as illustrated in Figure 20.
2. IN D IV ID U A L V A R IA T IO N D IS T A N C E . This di­
mension is a plus or minus variation of the N O M I ­
N A L A S S E M B L Y D IM E N S IO N on each individual
pinion (m arked on pinion - fig. 21) which m ay be
caused by m anufacturing variations.
3. C O R R E C T E D N O M IN A L D IM E N S IO N . This di­
mension is the N O M IN A L A S S E M B L Y D I M E N ­
S IO N plus or minus the IN D IV ID U A L V A R IA ­
T IO N D IS T A N C E .
Figure 2 0 — N o m in a l A sse m b ly D im e n sio n
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SH O P M A N U A L