Gear Tooth Contact Pattern Check; Gear Tooth Nomenclature; T E S - Chevrolet Chevelle 1977 Repair Manual

Fig. 4C -11--G ear T o o th N o m e n cla tu re

GEAR TOOTH CONTACT PATTERN CHECK

Prior to final assembly of the differential, a G ear Tooth
Contact Pattern Check is necessary to verify the correct
relationship between ring gear and drive pinion. G ear sets
which are not positioned properly may be noisy, or have short
life, or both. W ith a pattern check, the most desirable contact
between ring gear and drive pinion for low noise level and
long life can be assured.

Gear Tooth Nomenclature

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 center is the "heel" end. Toe end
of tooth is smaller than heel end. See Figure 4C-11.
FRONT WHEEL DRIVE
Test
1. Wipe oil out of carrier and carefully clean each tooth
of ring gear.
2. Use gear m arking com pound 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 bearing cap bolts to 55 lb. ft.
4. Apply a load until a torque of 40-50 lb. ft. is required
to turn the pinion.
NOTE:
give a satisfactory pattern. T urn companion flange with
wrench so that ring gear rotates one full revolution then
reverse rotation so that ring gear rotates one revolution
in opposite direction. Excessive turning of ring gear is
not recommeded.
5. Observe pattern on ring gear teeth and compare with
Figure 4C-12.
Adjustments Affecting Tooth Contact
Two adjustm ents can be made which will affect tooth
contact pattern. These are backlash and position of drive
pinion in carrier. The effects of bearing preloads are not
readily apparent on hand loaded teeth pattern tests: however,
these adjustm ents should be within specifications before
proceeding with backlash and drive pinion adjustments.
NOTE:
and backlash to obtain the correct pattern.
The position of the drive pinion is adjusted by increasing
or decreasing the shim thickness between the pinion head and
inner race of rear bearing. The shim is used in the differential
to compensate for m anufacturing tolerences. Increasing shim
thickness will move the pinion closer to centerline of the ring
gear. Decreasing shim thickness will move pinion farther
away from centerline of the ring gear.
Backlash is adjusted by means of the side bearing
adjusting shims which moves the entire case and ring gear
assembly closer to, or farther from the drive pinion. (The
adjusting shims are also used to set side bearing preload). To
increase backlash, increase right shim and decrease left shim
an equal am ount. To decrease backlash, decrease right shim
and increase left shim an equal amount.
The im portant thing to note is that the contact pattern
is centrally located up and down on the face of the ring gear
teeth.
A test made without loading the gears will not
It may be necessary to adjust both pinion depth
4C-7