AXLE-REAR
MOTOR TRUCK SERVICE MANUAL
Fig. 13-Fatigue Fracture-Misalignment.
The side gear shown in Fig. 13 is a very good example of
maximum strength of the material is exceeded and
failure resulting from misalignment in axle shafts. The
failure must take place. In most cases, the failure is not
same kind of failure is also frequently the result of an
instantaneous, but occurs over a period of time and is of
axle shaft breaking. If sprung or twisted and bent shafts
the progressive fatigue type. It may be attributed to
are not soon replaced after they have been damaged,
abusive operation and overloads.
the side gears may become mutilated adding
considerable parts cost to the repair job.
Generally a check of the conditions under which the
truck has been operated will very readily reveal the exact
Housings bent by accident or overload, through
circumstances causing the troubles.
misalignment carried to the differential, also cause
failures similar to the one shown.
It is not unusual for an axle shaft on the opposite side of
the vehicle to be damaged, bent, or sprung when one
The reason side gears fail in the manner seen above is
has failed. To eliminate the possibility of recurrent
that stresses are concentrated to localized areas. The
failures of the kind described and pictured here, it is
design and the computed strength of the gears are
always advisable to make sure both axle shafts are
based on the assumption that there will be no
examined and the housing is checked for correct
misalignment and the stresses to be carried will be
alignment.
spread over the entire splined area. When this is not
true,
the
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