Adjustments Affecting Tooth Contact - Chevrolet 1991 Light Duty Truck Repair Manual

4B2-12 8 1/2-INCH RING GEAR
1. Wipe all oil out of the carrier, and carefully clean
each tooth of the ring gear (figure 29).
2. Use gear marking compound 1052351 or equiva­
lent and apply this mixture sparingly to all ring
gear teeth, using a medium-stiff brush. When
properly used, the area of pinion tooth contact will
be visible when hand load is applied.
3. Tighten the bearing 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 without loading the gears will not
give a satisfactory pattern. Turn the pinion flange
with a wrench so that the ring gear rotates one full
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
compare this with figure 30.
ADJUSTMENTS AFFECTING
TOOTH CONTACT
Two adjustments 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 adjustments should be
within specifications before proceeding with backlash
and drive pinion adjustments.
The position of the drive pinion is adjusted by
increasing or decreasing the distance between the pin­
TOE CONTACT
INCREASE BACKLASH
HIGH FACE CONTACT
INCREASE PINION SHIM
ion head and the centerline of the ring gear. Decreas­
ing 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 which move the entire case and ring
gear assembly closer to, or farther from, the drive pin­
ion. (The adjusting shims are also used to set side
bearing preload).
p .
i l l
/
i l l
J j j
V
/ / / g
» j
I t
*
Figure 30—Gear Tooth Pattern
LOW FLANK CONTACT
DECREASE PINION SHIM
HEEL CONTACT
DECREASE BACKLASH
F2018