GMC 1989 Light Duty Truck, Repair Manual, Page: 185 / 998

lO ’ fe-INCH RING GEAR 4B4-9
5. If the reading is too high, rem ove the adjusting nut
locks, and loosen the right nut one slot, and tighten
the left nut one slot (figure 18).
6
. If the reading is too low, rem ove th e adjusting nut
locks, and loosen the left nut o ne slot, and tighten
the right nut one slot.
• T h e side b earing preload will rem ain set, as long as
the adjusting nut is tigh ten ed an eq u al am ou n t to
the nut which was loosened.
FINAL ASSEMBLY
- ►+ Install or C onnect (F igure 1)
Drive axles. R e fer to th e p roper service m anu al.
C over gasket (23) and cover (24) to the housing.
Cover bolts (25).
T ig h te n
• T h e cover bolts (25) to 2 7 N-m (20 ft. lbs.).
4. Axle housing to the vehicle. R e fer to th e proper
service m anual.
5. Lubricant to the rear axle.
GEAR TOOTH
PATTERN CHECK
C h ec kin g the ring ger to pinion tooth pattern is to be
d one only after setting up th e axle according to the
m ethods in this section. T h e pattern ch ec k is N E V E R to
be used as an initial ch eck, or instead of checking pinion
depth and backlash adjustm ents. T his ch eck is only to be
used to verify the correct ad ju s tm e n t of the g ear set after
setup.
1
. W ip e all oil out of th e carrier, and carefully clean
each tooth of the ring g e a r (figure 20).
2
. U se g ear m arking co m pond 1052351 or eq u ivalen t
and apply this m ixture sp aring ly to all ring g ear
teeth, using a m edium -stiff brush. W h e n properly
used, the area of pinion tooth contact will be visible
w hen hand load is applied.
3. T ig h te n th e b e a rin g c a p bolts to th e s p e c ifie d
torque.
4. E xp and th e brake shoes until a torque of 40 to 50 ft.
lbs. is required to turn the pinion.
A test m ade w ithout loading th e gears will not give a
satisfactory pattern. Turn the pinion flan g e with a
w re n c h so th a t th e rin g g e a r ro ta te s o n e full
revolution, th en reverse th e rotation so th at th e ring
g e a r rotates o ne revolution in the opposite direction.
5. O bserve th e pattern on th e ring g e a r teeth and
co m p are this with figure 21.
ADJUSTMENTS AFFECTING
TOOTH CONTACT
Two ad justm ents can be m a d e w hich will affect tooth
contact pattern: backlash , and the position of the drive
pinion in th e carrier. T h e effects of b earing prelo ad s are
not readily ap p are n t on hand loaded tooth contact pattern
tests; how ever, th e s e a d ju s tm e n ts sh o u ld be w ith in
specifications before p rec ee d in g with b acklash and drive
pinion adjustm ents.
T h e p o s itio n of th e d riv e p in io n is a d ju s te d by
increasing or d ecrea sin g th e d istan ce betw een the pinion
head and the cen te rlin e of the ring gear. T h e shim is used
in th e re a r a x le to c o m p e n s a te for m a n u fa c tu r in g
tolerances. D e creasin g the d istan ce will move the pinion
closer to th e cen terlin e of th e ring gear. Increasing th e
d is ta n c e will m ove the pinion fa rth e r aw a y from th e
cen terlin e of the ring gear.
B acklash is adjusted by m ean s of th e side b earing
adjusting shim s an d /o r adjusting nuts, w hich m ove th e
entire case and ring g e a r assem b ly closer to, or farth e r
from , the drive pinion. (T h e adjusting shim s are also used
to set side b earing p relo ad .)
If the th ickn ess of the right shim is increased (along
with d ecreasing th e left shim thickness), b acklash will
increase.
T h e b acklash will d e crea se if the left shim th ickn ess is
increased (along with a d ecrea se in right shim thickness).