Gear Tooth Contact Pattern Check; Carrier Case Assembly - GMC 1989 Light Duty Truck Repair Manual

4C4-16 K TRUCK FRONT AXLE
Example: A dial indicator reading of 0.16 mm means
that there is actually 0.08 mm backlash.
6 . Follow the steps for adjusting backlash outlined
previously.
GEAR TOOTH CONTACT
PATTERN CHECK
Before final assembly of the differential, a gear tooth
contact pattern check should be performed.
It should be noted that a gear tooth contact pattern
check is NOT a substitute for adjusting pinion depth and
backlash as previously outlined. It is a final check to verify
the correct running position of the ring gear and the drive
pinion. Gear sets which are not positioned properly may
be noisy, or have a short life, or both. With a pattern
check, the best contact between 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 33).
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 m edium stiff brush. When
properly used, the area of pinion tooth contact will
be visible when hand load is applied.
3. Apply a load until a torque of 54-70 N
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.
E x c e s s iv e
recommended.
4. Observe the pattern on the ring gear teeth and
compare with figure 34.
ADJUSTMENTS AFFECTING TOOTH CONTACT
Two adjustments can be made which will affect the
tooth contact pattern. These are backlash and the
position 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 adjustm ents
should be within specifications before proceeding wiht the
backlash and the drive pinion adjustments.
It may be necessary to adjust both pinion depth and the
backlash to obtain the correct pattern.
The p o sitio n of the drive p in io n is adjusted by
increasing or decreasing the shim thickness between the
pinion head and the inner race of the rear bearing. The
shim is used in the d iffe re n tia l to com pensate for
manufacturing tolerances. Increasing the shim thickness
will move the pinion closer to the centerline of the ring
gear. Decreasing the shim thickness will move the pinion
farther away from the centerline of the ring gear.
Backlash is adjusted by means of the side bearing
adjusting sleeves which move the entire case and ring
gear assembly closer to, or farther from the drive pinion.
(The adjusting sleeves are also used to set side bearing
preload). To increase backlash turn the left sleeve in and
turn the right sleeve out an identical amount. To decrease
backlash, turn the right sleeve in and turn the left sleeve
out an identical amount.
It is important that the contact pattern be centrally
located up and down on the face of the ring gear teeth.

CARRIER CASE ASSEMBLY

Install or C onnect (Figures 1 through 4)
Bend the lock (51) over the sleeves (32). (Right side
only on K35 models).
Bolt (64) and lock (63) (K35 models).
Rem ove or D isconnect (Figures 1 through 4)
1. Bolts (28).
2. Right carrier case half.
Clean
C a rrie r case and axle tube sealing surfaces.
Remove all grease and oil. Use carburetor cleaner
or equivalent.
Install or C onnect (Figures 1 through 4, 19,
and 35).
Tools Required:
(40-50 ft.
tti
tu rn in g of th e rin g
J 36600 Output Shaft Seal Installer (K15-25)
J 22833 Output-Shaft Seal Installer (K35).
J 33842 Pilot Bearing Installer
J 36616 Bushing Replacer Set
g e a r is n ot