Pontiac tempest 1968 Service Manual page 136

S T A N D A R D D I F F E R E N T I A L
4A-13
The position of the drive pinion is adjusted by
increasing or decreasing the shim pack between the
pinion head and inner race of rear bearing. The shim
pack is used in the differential to compensate for
manufacturing tolerances. Increasing shim pack
thickness will move the pinion closer to centerline of
the ring gear; decreasing shim pack thickness will
move pinion farther away from centerline of the ring
gear.
E F F E C T S O F BACKLASH ON TOOTH P A T T E R N
The terms "excessive" and "insufficient" refer to
settings which are greater than .009" or less than
.005" as specified. With respect to tooth contact
patterns, "excessive" refers to backlash which, a l ­
though less then .009", is more than necessary to
provide the desire pattern. Similarly, "insufficient"
refers to backlash which, although .005" or more, is
less than necessary to provide the desired pattern.
Provided the pinion is properly positioned, excess
backlash will give a high heel pattern on both drive
and coast sides (Fig. 4A-17). Decreasing backlash by
moving the case and ring gear assembly closer to
the pinion will cause the pattern to move toward the
toe end and down toward center of the tooth on both
drive and coast sides.
Insufficient backlash, provided the pinion is prop­
erly positioned, will give a low toe pattern on both
drive and coast sides (Fig. 4A-18). Increasing back­
lash will cause the pattern to move toward the heel
end and up toward top of the tooth on both drive and
coast sides.
T O E
/ \
4
HEEL HEEL
DRIVE SIDE C O A S T SIDE
( C O N V E X ) ( C O N C A V E )
F i g . 4 A - 2 0 Effect on Pattern - As Shim
Thickness is Increased
side (Fig. 4A-19), provided backlash is within speci­
fications of .005" to .009". Moving the pinion closer
to centerline of the ring gear by increasing shim
pack thickness will cause the high heel contact on
drive side to lower and move toward the toe; the
high toe contact on coast side will lower and move
toward the heel (Fig. 4A-20).
When the pinion is too close to the ring gear, the
pattern will be a low toe contact on drive side and
a low heel contact on coast (Fig. 4A-21), provided
backlash is within specifications of .005" to .009".
Moving the pinion farther away from the ring gear
by decreasing shim pack thickness will cause low
toe contact on drive side to raise and move toward
the heel; low heel contact on coast will raise and
move toward the toe (Fig. 4A-22).
E F F E C T S O F PINION POSITION
ON TOOTH P A T T E R N
When the drive pinion is too far away from center-
line of the ring gear, the pattern will be a high heel
contact on drive side and a high toe contact on coast
T O E
/ \
HEEL
i ^ : . . .......
1 .
v
HEEL
DRIVE SIDE
C O A S T SIDE
( C O N V E X )
( C O N C A V E )
F i g . 4 A - 1 9 Tooth Pattern - Pinion Too Far Away From
Ring G e a r (Shim Thickness Insufficient)
OVERHAUL DIFFERENTIAL
REMOVE D I F F E R E N T I A L CASE
NOTE: Before removing case from housing, be
sure the checks under pre-repair investigation
have been completed.
T O E
HEEL HEEL
DRIVE SIDE C O A S T SIDE
( C O N V E X ) ( C O N C A V E )
F i g . 4A-21 Tooth Pattern - Pinion Too Close to Ring G e a r
(Shim Thickness Excessive)