Gear Tooth Contact Pattern Check - GMC 1989 Light Duty Truck Repair Manual

Tighten
• The bolts to 80 N m (60 ft. lbs.)
6. Check and record the backlash at three or four
points around the ring gear.
• The pinion m ust be held stationary when
checking backlash.
• The backlash should be the same at each
point w ithin 0.05 mm (0.002-inch). If the
b a c k la s h v a rie s
(0.002-inch), check for burrs, a distorted case
flange, uneven bolting conditions, or foreign
matter between the case and the ring gear.
7. The backlash at the minimum lash point measured
should be between 0.13 and 0.23 mm (0.005 and
0.009) for all new gear sets, 0.08 and 0.28 mm (0.003
and 0.011-inch) for used gear sets.
8. If the backlash is not within specifications, move the
ring gear in or out from the pinion by increasing the
th ic k n e s s of one s h im , and d e c re a s in g the
m o re th a n 0.05 mm
V -INCH RING GEAR 4C1-11
8 2
thickness of the other shim by the same amount.
This will maintain the correct front axle side bearing
preload.
• Moving 0.003-inch worth of shims from one
side of the differential to the other will change
the backlash adjustm ent by approxim ately
0.002-inch.
9. Recheck the backlash and correct as necessary.
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
veryify 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 tooth is smaller than the heel
end, (figure 25).
TEST
1. Wipe oil out of carrier and carefully clean each tooth
of the ring gear.
2. Use gear marking compound 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 specifications.