Chevrolet 1988 Light Duty Truck Repair Manual page 163

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 n ch so th a t the 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 26.
TOE CONTACT
INCREASE BACKLASH
8
ADJUSTMENTS AFFECTING
Two adjustm ents can be made which 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, these a d ju stm en ts shou ld 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. D ecreasing the
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 means of the side bearing
adjusting shims 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 sh im s are also used to set side be arin 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).
Figure 26 — Gear Tooth Pattern
V -INCH RING GEAR 4B2-11
2
TOOTH CONTACT
LOW FLANK CONTACT
DECREASE PINION SHIM