Chevrolet 1991 Light Duty Truck Repair Manual page 285

the ring gear and the drive pinion for low noise level
and long life can be assured.
GEAR TOOTH TERMS
The side of the ring gear tooth which curves outward,
or is convex, is referred to as the "drive" side. The
concave side is the "coast" side. The end of the tooth
nearest center of ring gear is referred to as the "toe"
end. The end of the tooth farthest away from the center
is the "heel" end. The toe end of the tooth is smaller
than the heel end (figure 32).
TEST
1. Wipe oil out of carrier and carefully clean each
tooth of the ring gear.
2. Apply gear marking compound sparingly to all ring
gear teeth using a medium stiff brush. When prop­
erly used, the area of pinion tooth contact will be
visible when hand load is applied.
3. Using a torque wrench, apply a load until a torque
of 54-70 N-m (40-50 ft. lbs.) is required to turn the
pinion.
A test made without loading the gears will not
give a satisfactory pattern. Turn the companion
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. Excessive turning of the ring gear is not
recommended.
4. Observe the pattern on the ring gear teeth and
compare with figure 33.
TOE CONTACT
INCREASE BACKLASH
HIGH FACE CONTACT
INCREASE PINION SHIM
8 1/4 AND 9 1/4-INCH RING GEAR 4C4-15
ADJUSTMENTS AFFECTING TOOTH CONTACT
Two adjustments can be made which will affect the
tooth contact pattern. These are backlash and the posi­
tion of the drive pinion (pinion depth) in the carrier. The
effects of bearing preloads are not easily seen on hand
loaded teeth pattern tests. These adjustments should
be within specifications before proceeding with the
backlash and the drive pinion adjustments.
It may be necessary to adjust both pinion depth and
the backlash to obtain the correct pattern.
Figure 33—Gear Tooth Contact Pattern
Figure 32—Gear Tooth Terms
LOW FLANK CONTACT
DECREASE PINION SHIM
HEEL CONTACT
DECREASE BACKLASH
F2018