The news scimitar. (Memphis, Tenn.) 1907-1926, 1920-03-27

srly fabricated the trouble usually Is
that the hevei pinion on the drive shaft
and the large bevel ring gear on the
aifferentlal housing are not so posi-
toned that their teeth mesh together
properly, and adjustments should be
made to correct this condition when
ever a rear axle runs noiSily, as It
may do because OF wrong factory ad-
justment, the loose ming Of locking de-
vices, wear in parts or unskillful as
sembling after overhaulings, The de
tails OF this process vary WILDLY with
different axle designs and the procedure
Is delicate enough 20 render expert AS
kistanee often desirable. but the gem
eral principles involved are common TO
sll gear driven aNles and not difficult
to understand. II is plain that the
two gears should h. so positioned that
the full length OF the teeth Of one shall
engage with the teeth Of the ether, that
Is that the teeth OF one should not
overlap those OF the other, for In that
case a portion of the tooth strength
of both gears would not be utilized and
breakaTe would be more likely to uC-
cur. No pair Of geas operates quietly
and Economically unless the teeth OF
the one enter the tooth spaces Of the
other to exactly the correct depth.
Otherwise there Is undue sliding con-
tact, causing loss Of power. excessive
wear and noise Moreover, IL they do
not mesh deeply enough only a part
of the tooth strength Is utilized and
stripping" or brcakage becomes more
likely, The object OF driving gear ad
iustment is thus to secure full face
mesh Of the pinion and gear and TO
obtain a permanent and correct depth
Of mesh between them There is al
ways q tendency to push apart In the
case OF two gears that are running In
mesh and. in the case of pair Of
bevel gears, running upon two shafts
az right angles, this force is diNided in
ing TO force the pinion forward on the
propeller shaft and the other to force
the large gear and dlfferential away
from the pinion.
In order to resist the tendency Of
the driving plnion TO move forward and
that OF the large bavel gear TO shift
to the left out of their correct positions
or, in orth4r words, to resist the end
thrusts upon the propeller shaft and
upon the differential gear. thrust
bearing Is fixed in the propeller shaft
housing and another in the fixed po-
sition OF the axle housing, known as
the differential carrier, In fact, a pair
az bearings capable Of resisting end
motion Is often provided, one upon
either side OF the bevel pnion and an
other pair is always provided one upon
each side OF the 1ifferential. these bear
ings being additional TO those required
y resist bending rresses upon the
shafts, When the thrust bearings arc
correctly adjusted, no appraclable end
wise motion nf either the pinion or OF
ltle large hevel gear and the differen-
tial easing which carries Il is permit
ted and the two gears run In perfect
mesh. When. however through any
cause, the two gears cease to mesh to
exactly the correct depth or their faces
fail to line up perfectly IL is these
thrust bearings which must he adjust
Cd, as they are the means by which
the relative position OF the two gears
u determined. Modern rear axle hous-
ings have large plates which, when
removed give access TO the difreren-
tlai thrust BEARINGS and the pinion
thrust bearings are usually adjustable
by moving the whole pinion housing
with relation TO the axle housing. The
usual test for correct depth OF mesh
Is TO apply thick white paint 10 a few
teeth Of the ring gear II when these
are meshed with the pinion, the teeth
OF khe latter are whitened nearly their
whole length, the setting is approx
nlateiy correct