GMC 1982 Light Duty Truck Service Manual page 459

Fig. 4B3-10--Pinion Code Location
used during d eterm inatio n of side bearing shim
requirements.
Pinion Shims
Ring gears and pinions are supplied in matched sets
only. M atching numbers on both pinion and ring gear are
etched for verficiation. If a new gear set is being used, verify
the numbers of each pinion and ring gear before proceeding
with assembly.
On the rear face of each pinion there is etched a plus
( + ) number, a minus (-) number, or a zero (0) number,
which indicates the best running position for each particular
gear set. This dimension is controlled by the shimming
behind the inner bearing cup. W henever baffles or oil
slingers are used, they become a part of the adjusting shim
pack.
F o r example: if a pinion is etched + 3, this pinion
would require .003" less shims than a pinion etched "0" .
This m eans by removing shims, the mounting distance of
the pinion is increased by .003" which is ju st what a +
etching indicates. Or if a pinion is etched - 3 , we would
w ant to add .003" more shims than would be required if the
pinions were etched " 0 " . By adding .003" shim s, the
mounting distance of the pinion was decreased 003" which
is ju s t what a - 3 etching indicated. Refer to figure 4B3-10.
If the old ring and pinion set is to be reused, measure
the old shim pack and build a new shim pack to this same
dimension. If baffle is in the axle assembly, it is considered
as part of the shim pack.
To change the pinion adjustment, shims are available
in thicknesses of .003", .005" and .010".
If baffle or slinger is bent or mutilated, it should be
replaced.
M easure each shim separately with a micrometer and
add together to get total shim pack thickness from original
build up.
If a new gear set is being used, notice the plus or minus
etching on both the old and new pinion, and adjust the
thickn ss of the old shim pack to com pensate for the
difference of these two figures.
For example: If the old pinion reads ( + 2) and the
pinion is (-2), add .004" shims to the original shim pack.
DRIVE P IN IO N
Assem bly a n d In sta lla tio n
1. Determine the correct pinion depth shim by using the
chart in figure 4B3-9.
2. Install the pinion depth shim in rear cup bore.
3. Install rear bearing cup by using driver handle J-8092
and installer J -2 4 3 8 1.
4. To the outer shim pack (for setting preload) add or
remove an equal amount as was added or removed from
the inner shim pack.
5. Install outer cup in carrier bore, using installer J-7818
with Drive Handle J-8092.
6. Press rear pinion bearing onto pinion shaft, using
installer J-24433.
7. Install drive pinion and bearing into the differential
carrier.
8. Install preload shims and front pinion bearing. Do not
install oil seal at this time.
9. Install flange and holding bar J - 8 6 14-11 as shown in
" Drive Pinion - Rem oval".
10. Install washer and nut onto pinion shaft. Torque nut to
350 N-m (250 lbs.) ft.
11. Remove holding bar and with an inch pound torque
wrench m easure rotating torque. R otatin g torque
should be 10 to 20 in. lbs. with original bearings or 20 to
40 in. lb. with new bearings.
T orque reading to s ta rt shaft turning must be
disregarded.
12. If torque requirem ents
specifications, adjust shim pack as necessary.
• To increase preload, decrease the thicknes of preload
shims.
• To decrease preload, increase the thickness of
preload shims.
13. W hen bearing preload meets specifications, remove
nut, washer and flange from pinion shaft.
14. Install new pinion oil seal into housing as shown in
figure 4 B 3-11, using J-24384.
15. Install flange, washer and nut. Using holder bar
Fig. 4B3-11 — Installing Pinion Oil Seal
REAR A X LE 4 B 3 -5
(preload) are not to