MOTOR TRUCK SERVICE MANUAL
Fig. 11-Scoring and Seizure of Spider and Pinions
A typical example of seizure in the differential is seen in
Fig. 11. This unit operated for some time after scoring
Off-the-highway service such as logging, oil field hauling
first started and the spider arms as well as the differential
and construction work, produces most failures of this
pinions were badly discolored by the heat generated.
kind, although they are also found in highway work
The fact that there was metal-to-metal contact is clearly
during the winter months when roads, are spotted with
Actual experience has proved failures of this kind are
Good quality recommended lubricants will go a long way
caused by one of three circumstances or a combination
toward eliminating differential seizures but will not
of them. Relative to frequency of occurrence, they are
prevent them in cases of excessive wheel spinning.
wheel spinning, inadequate lubrication, and overstress.
Overloading where ground conditions are bad is
All have a common factor in the loss of lubricating film
especially conducive to wheel spinning. It is well in
between the adjacent surfaces. Without oil protection,
analyzing differential failures to check payloads and
friction causes the hardened areas to overheat, score
and finally, if running is continued, to seize.