To measure ring and pinion backlash, position a
dial indicator stem on one of the ring gear teeth. Then,
while holding the pinion gear STATIONARY, wiggle
the ring gear back and forth. Indicator needle
movement will equal gear backlash. Compare your
measurements to the manufacturers specifications and
adjust as needed.
Backlash adjustment can be made by adjusting
nuts or by moving shims from one side to the other. To
increase backlash, move the ring gear away from the
pinion gear. To decrease backlash, move the ring gear
towards the pinion gear.
RING AND PINION TOOTH CONTACT
PATTERN.The ring and pinion tooth contact
pattern is used to double-check ring and pinion
To check the accuracy of your adjustments, coat
the ring gear teeth with a thin coat of red lead, white
grease, hydrated ferric oxide (yellow oxide or iron), or
Prussian blue. Turn the ring gear one way and then the
other to rub the teeth together, producing a contact
pattern on the teeth. Carefully note the contact pattern
that shows up on the teeth where the substance used has
been wiped off.
A good contact pattern is one located in the center
of the gear teeth (fig. 5-21). Figure 5-21 shows several
ring and pinion gear contact patterns. Study each and
note the suggested correction for the faulty contact.
Note the names of the areas on the ring gear. These
include the following:
TOE (narrow part of the gear tooth)
HEEL (wide part of the gear tooth)
DRIVE SIDE (convex side of the gear tooth)
COAST SIDE (concave side of the gear tooth)
When used gears are adjusted properly, the contact
pattern will vary from that of new gears. The important
thing to keep in mind with used gears is that the pattern
should be closer to the toe than the heel of the tooth, as
shown in figure 5-21. Notice that the ideal tooth pattern
on new teeth is uniform on both sides, whereas the used
gear indicates considerably more contact on the
Once you have obtained the proper adjustment on
the ring and pinion, bolt the carrier housing in place.
Make sure you use a new gasket. Tighten the bolts
according to the manufacturers specifications to
prevent them from working loose. Reinstall the axle
shafts and new gaskets. Reconnect the drive shaft and
fill the axle housing with the proper lubricant.
REVIEW 2 QUESTIONS
must be capable of
providing torque to both axles when turning
Figure 5-21.Tooth contact patterns.