Chevrolet CAMARO 1979 Service Manual page 370

48-4 REAR AXLE
indicat€ fâilure of rhe unit.
Duing regular operâtion (straight ah€ad driving) when
both wheels rotâte at equâl speeds, there is an approximârety
equal driving lorc€ delivered ro each wheel_ When
cornering, the inside wheel delivers extra driving force
câusing slippage in borh clutch packs. Consequently, rhe
operational life of the limited slip unir is dependenr upon
equal rotation of boih wheels dudng straight âh€âd
operation. If wheel rotation for both rear wheels is nor equal
during straight ahead operarion the limited slip unit will
constantly be functioning as if the car were comering. This
will impose constant slippâge on the clurch pâcks and wiil
eventually iead to abnormâl wear on tÏe clutch pack, or
cone. Therefore. il is imporanr ihar rhere be no excessive
differences in the rear wheel tire sizes, air pressures, or tire
wear patterns. One indicâtion ofthis condition is "stverving
on acceleration", If swerving on acceleration is encountered,
check the rear wheejs for dillerenl lire size. air pressure, or
excessively different wear pattems, and ircad depths, belore
proceeding inlo an overhaul operation.
R E A R A X L E P R E - R E P A I R D I A G N O S I S
A close exâminâtion of the differential prior to
disass€mbly will ofteû reveal valuable information as to the
extent and type of repairs or adjustments necessâry. The
information thus gained, coùpled with the report of
malfunctioning, will provide â basis for determining the
degree ofdisassembly requir€d. Since ftequent cause ofaxle
noise are improp€r backlash, pinion beâing preload, or side
bearing preload, or acombinalion, a few simpie adjustments
may be all that are necessary to correct a problem.
Therefore, before removing the differential from the
housing, the following checks should be made with the
r€sults recorded and analyzed: 1) Backlash; 2) Total
Assembly Preload; and 3) Tooth Contâct Pâttern Test.
Use câre at all times to keep din ând other foreign
matter, such as grinder dust, soot, or sand, away from
differentiâl to prevent possibility of subsequent failur€.
The pinion ând dng gear must be complerely
âssembled, instâlled, and all preload and bâcklash
adjustments completed prior to th€ start of this method of
pinion depth settiûg. The following procedure can be used
in place of the gâge method of pinion depth setting.
Gear Tooth Nomenclature
The side ofthe ring gear tooth which curves outward,
or is coûvex, is r€ferred to as the "drive" side. The concave
side is th€ "coast' side. The end ofthe tooth nearesr cenrer
of ring gear is relerred to as the "toe" end.
The end of rhe tooth fânhes! âway from center ls !h€
"heel" end. Toe end of tooth is smalle. than heel end. It is
v€ry important that tooth contacr be tesred before the rear
axle carrier âssembly is disassembled. Variâtions in the
cârrier or pinion rear bearing may câuse the pinion ro be
too far âway from, or closeto, the ring gear. Thus, the toorh
contâct must be t€sled ând corrected, if necessary, or the
gears mây be nolsy.
Tooth Contact Pattern Test
l. Wipe oil out ofcarrier ând carefully clean each toolh
of ring geâr.
2. Use gear marking compound 1052351 or equivalent
and apply this ûixture sparingly to âll ring gear teeth, using
a m€dium stiff brush. When prop€ y used, the ârea
Dinion tooth conhcr will be visible when hand loâd
applied.
3. Tighren bearing cap bolrs ro 55 ft. lbs., (47 ft. lbs.
on "B" axles with bame).
4. Expand brake shoes until a torque of40 to 50 ft. lbs.
is required to turn the pinion.
A lest made without ioâding the gears will not give â
satisfactoiy pattern. Tum pinion flange with wrench so that
ring gear rotates on€ full revolution, then reverse roration
so thât ring gear rotâtes one revolulion in opposite direction.
5. Observe pâttem on ting gear teelh and compare i{ith
Figs. 4B-3 and 4B-4.
Effects of Increasing Load on Tooth Contact
Pattgrn
When "loâd" on ring and pinion gear is increased, such
as when car is âccelerated forwârd from stândstill or from
normal drive, the tooth contact will tend to spread out and,
under very heavy loâd, will extend fron near toe to near
heel on the ddv€ side. The entire contâct âlso tends to shifr
toward heel under incrcâsingly heâvier loâds and will
becomesomewhat broâder with rcspect to lops and bottoms
ofteeth. The pâtterns obtâined by this tooth contâct pâttern
test approximâte a light load ând, for this reason, they will
extend only âbout halfway.
The importânt thing to note is that the contad padern
is c€ntrally located up ând down on the face of the ring gear
Adiustments Affecting Tooth Contact
Two adjustments can be mâde ivhich will afiect tooth
contacl parrern, backla\h, and posirion of dri\e pinion rn
carrier. The effects of beâring preloads â!e not reâdily
appârent on (hândloâded) tooth contâct pâttern tests;
however, these âdjustments should be within specifications
before proceeding with backlash and drive pinion
Backlash is adjusted by meâns of the side beâring
adjusting shims which moves the entire case and rirg gear
âssembly closer to, or farther ftom, the drive pinion. (The
âdjusting shims are also used to set side bearing preload.)
The position of the drive pinion is adjusted by increasing
ôr decreasing the shim thickness between the pinion head
and inner race ofred bearing. The shim is ùsed in the rear
axle to compensate for manufâctùring tolerânces.
Increasing shim thickness will move the pinion closer to
centerline of ahe ring geâr. Dec.eâsing shim thickness will
move piûion farther awây from centerline ofthe ring gear.
Effects of Pinion Position on Tooth Pattefn
When the drive pinion is too fâr away from centerlrne
of the ring gear, the pâ$ern will be â high heel contâct on
the drive side ând high toe contâct on coast side. (Fig. 4B-5)
Moving the pinion closer to centerline of the ring gear by
increasing shim thickness will cause the high heel contâct
on drive side to lower and move ioward the toej the high
to€ contact on coâst side will lower and move toward the
heei. (Fig. 48-6)
When the pinion is too close to the centerline of the
ring geâr, the patlem witi be â low toe contâci on d.ive side,
âDd a low heel contact on coâst- (Fig. 4B-7) Moving the
pinion farther âwây from the ling gear by decreasing shim
of
is