The effects of contamination on bearing life have recently commanded a great deal of attention. This paper will illustrate how to apply existing contamination theories to an actual application. Many factors must be considered when designing a gearbox, such as: the duty cycle, frequency of maintenance, temperatures, and the operating environment. These factors may lead to a condition that might severely impede the longevity of a particular vehicle. The following information will provide the designer increased flexibility in choosing the correct bearing for any application.