AGMA procedures with cast-iron gear pairs differ from those with steels because life predictions are difficult; consequently (YN) P, (YN) G, (ZN) P, and (ZN) G are set to unity. The consequence of this is that the fatigue strengths of the pinion and gear materials are the same. The reliability is 0.99 and the life is 107 revolution of the pinion (KR = 1). For longer lives the reducer is derated in power. For the pinion and gear set of Prob. 14–24, use grade 40 cast iron for both gears (HB = 201 Brinell). Rate the reducer for power with SF and SH equal to unity.