Effects Of Increasing Load On Tooth Contact Pattern; Differential Cranking Tool; Desired Tooth Contact Under Light Load; Adjustments Affecting Tooth Contact - Pontiac Grand Prix Service Manual

STANDARD DIFFERENTIAL 4A-13
DIA.
R00 APPROX. 6 LONG.
WELO SECURELY
Fig.
4A-15
Differential Cranking Tool
while turning, apply pressure to back side of ring gear
by hand (a leather glove can be used). A test made
without loading the gears will not give a satisfactory
pattern. Turn companion flange 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 may indicate good tooth
pattern because one or two teeth are making proper
contact.
NOTE: The crank in Fig. 4A-IS may be easily made as
follows: a. Weld a
Y
8 " heavy duty Jut washer to a piece
of 1/4" diameter rod, approximately 6 " long, and form
as shown. b. Tap door knob for 38" bolt and attach
knob to crank as shown. Leave bolt loose enough to
permit knob to turn.
4. Closely inspect tooth pattern on ring gear to
determine whether pressure lines are apparent.
NOTE:
If
observation reveals pressure lines are present
(dark narrow band at edge of pattern), examine for pressure
line position on drive and coast sides of ring gear. If lines
on drive side are too deep and those on coast side are too
high (near heel and toe respectively), additional shims to
bring pinion gear out (providing a more centrally located
tooth pattern on ring gear) will result in a noisy tooth
contact. This occurs because the pressure line has been
moved deeper into the tooth on the drive side and farther
out qn the coast side. It does not follow that the ring gear and
pinion are not good or should be destroyed. It only means
they will not operate quietly in the carrier in which they
are presently installed. These same parts may operate
quietly in another carrier when tooth pattern is checked.
Removing backlash moves ring gear into pinion gear,
driving the pinion deeper into the ring gear. Whenever
pressure lines are noted, as explained above, install
another ring gear and pinion set.
5. Observe pattern on ring gear teeth and compare
with Fig. 4A-16.
TOE
HEEL HEEL
DRIVE SIDE COAST SIDE
(CONVEX) (CONCAVE)
Fig.
4A-16
Desired Tooth Contact Under Light Load
TOE
HEEL HEEL
DRIVE SIDE COAST SIDE
(CONVEX) (CONCAVE)
Fig.
4A-17
Tooth Pattern
-
Excessive Backlash
EFFECTS OF INCREASING LOAD ON TOOTH
CONTACT PATTERN
When "load" on ring and pinion gear is increased,
such as when car is accelerated from standstill or from
normal drive, the tooth contact will tend to spread out
and under very heavy load will extend from near toe
to near heel. The entire contact also tends to shift
toward heel under increasingly heavier loads and will
become somewhat broader with respect to tops and
bottoms of teeth. The patterns obtained by red lead
tests, dependent upon degree of "loading", approxi-
mate a normal light load. For this reason, they will
extend only about halfway (Fig. 4A-16). The impor-
tant thing to note is that the contact pattern is
centrally located up and down on the face of the
ring
gear.
ADJUSTMENTS AFFECTING TOOTH CONTACT
Two adjustments can be made which will effect tooth
contact pattern: backlash and position of drive pinion
in camer. The effects of bearing preloads are not
readily apparent on (hand loaded) red .lead tests: