Chevrolet 1977 10 Series, Repair Manual, Page: 108 / 468

4B-36
OVERHAUL MANUAL
Fig. 26C—Gear Tooth N om enclature
4. E xpand brake shoes until a torque o f 20-30 lb. ft. is
req u ired to turn the pin io n .
N O T E : A test m ade w ith o u t lo ad in g the
g ears will not give a satisfacto ry p a tte rn .
T u rn com panion flange w ith w rench so th at
rin g g ear rotates one full revolution then
reverse ro tatio n so th a t rin g g ear ro tates one
revolution in opposite direction. Excessive
tu rn in g o f rin g gear is n o t recom m ended.
5. O bserve p atte rn on rin g g e a r teeth and com pare
w ith Figure 27C.
Adjustments Affecting Tooth Contact
Two adjustm ents can be m ade w hich will affect tooth
contact p atte rn . These are backlash and po sitio n o f drive
p in io n in carrier. T he effects o f b e a rin g p relo ad s are not
readily a p p a re n t on h an d loaded teeth p a tte rn tests:
however, these adjustm ents should be w ith in specifica­
tions before p roceeding w ith backlash and drive p in io n
adjustm ents.
N O TE: It m ay be necessary to adjust both
p inion d ep th and backlash to o b ta in the
correct p attern .
The position o f the drive p in io n is adjusted by
increasing or d ecreasing the shim thickness betw een the
pinion head and in n e r race o f re a r b earin g . T he shim is
used in the differential to co m p en sate for m an u factu rin g
tolerances. Increasing shim thickness will move the
p in io n closer to centerline o f the rin g gear. D ecreasing
shim thickness will move p in io n fa rth e r away from
centerline o f the ring gear.
Backlash is adjusted by m eans o f the side b earin g
adjusting shim s w hich moves the e n tire case and ring
gear assem bly closer to, or fa rth e r fro m the drive pinion.
(The adjusting shim s are also used to set side b earing
preload). To increase backlash, in crease rig h t shim and
decrease left shim an equal am o u n t. To decrease
backlash, decrease rig h t shim a n d increase left shim an
equal am ount.
T he im p o rta n t th in g to note is th a t the contact p a tte rn is
centrally located up and down on the face o f the ring
gear teeth.