MOTOR TRUCK SERVICE MANUAL
Fig . 6-Overheated Gear Set .
A typical example of a ring gear and pinion subjected to
available, thus causing the surfaces to overheat because
prolonged excessively high temperatures is seen in Fig.
6. Note that the pinion bearing fused to the pinion. The
ring gear teeth will show definite discoloration due to the
A good quality lubricant would provide the proper oil film
heat generated. Metal-to-metal contact is very evident
under heavy loads to prevent excessive overheating. A
by the distorted condition of the pinion.
result of using contaminated lubricants may be seen by
the evident end roll at the pinion pilot bearing. This
Actual experience has shown that this type of failure is
condition developed because the lubricant could not
caused by one of three circumstances or a combination
withstand the heat generated by heavy loadings at the
of them. They are: improper lubricant, low lubricant
level, and infrequent lubricant change. When one or
more of these conditions are present, the proper
From the above discussion, it is evident that proper
lubrication film between contacting metal surfaces is not
lubrication maintenance is one of the essentials for
proper gear set life.