Gear Tooth Pattern C H E C; Adjustm Ents Affecting Tooth C O N Ta C - Chevrolet 1988 Light Duty Truck Repair Manual

4B1-10 AND 7
7 1/2
Figure 18— Gear Tooth Nom enclature
GEAR TOOTH
PATTERN CHECK
C hecking the ring gear to pinion tooth pattern is to be
done only after setting up the axle according to the
m ethods in this section. The pattern check is NEVER to
be used as an initial check, or instead of checking pinion
depth and backlash adjustments. This check is only to be
used to verify the correct adjustm ent of the gear set after
setup.
1. W ipe all oil out of the carrier, and carefully clean
each tooth of the ring gear (figure 18).
2. Use gear m arking com pound 1052351 or equivalent
and apply this m ixture sparingly to all ring gear
teeth, using a m edium -stiff brush. W hen properly
used, the area of pinion tooth contact will be visible
when hand load is applied.
3. T ig hten the b e a rin g cap bolts to the specified
torque.
4. Expand the brake shoes until a torque of 40 to 50 ft.
lbs. is required to turn the pinion.
A test made w ithout loading the gears will not give
a satisfactory pattern. Turn the pinion flange with a
w re nch so th a t th e ring g e a r rotates one fu ll
revolution, then reverse the rotation so that the ring
gear rotates one revolution in the opposite direction.
5. Observe the pattern on the ring gear teeth and
com pare this with figure 19.
ADJUSTMENTS AFFECTING
TOOTH CONTACT
Two adjustm ents can be made w hich will affect tooth
contact pattern: backlash, and the position of the drive
pinion in the carrier. The effects of bearing preloads are
not readily apparent on hand loaded tooth contact pattern
tests; however, th e se a d ju stm en ts should be w ithin
specifications before proceeding with backlash and drive
pinion adjustments.
T he p o s itio n of th e d riv e p in io n is a d ju s te d by
increasing or decreasing the distance between the pinion
head and the centerline of the ring gear. Decreasing the
/a-INCH RING GEAR AXLES
5
distance will move the pinion closer to the centerline of
the ring gear. Increasing the distance will move the pinion
farther away from the centerline of the ring gear.
Backlash is adjusted by m eans of the side bearing
adjusting shim s w hich move the entire case and ring gear
assem bly closer to, or farther from, the drive pinion. (The
a d ju s tin g shim s are also used to set side b e a rin g
preload).
If the thickness of the right shim is increased (along
with decreasing the left shim thickness), backlash will
increase.
The backlash will decrease if the left shim thickness is
increased (along with a decrease in right shim thickness).