29.923 is endurance, which evaluates wear and general durability - different than fatigue. Fatigue comes from 29.571. The regulation does not specify handling any different for gears, but the AC does have an entire section on gear fatigue. It is intended, as it states, to be specifically for gear tooth bending, however it does mention that "fatigue damage other than tooth fatigue should be considered for test validity and the integrity of the affected part confirmed as necessary" The pinion rim failure mode should now, if it was not originally, be considered a catastrophic failure mode. This would then necessitate that the fatigue evaluation be conducted for it using the non-gear guidance -which will be quite complicated. Why? besides multiple specimen, 3 sigma, the initiation is coming from a bearing integral raceway. This gets tricky now, as the puma family is not certified to the latest damage tolerant standards, so the evaluation could simply assume surface finish as new. A little bearing wear, lubrication concerns, and/ or load changes, make this a complicated scenario. If there is no replacement time for the pinion, then they could be re-using pinions at overhaul with an unknown number of hours. Of course we still don't know if this is an early symptom, or the root cause.