A gearbox for an auxiliary power unit (APU) includes features that prevent submersion of gears in lubricant in extreme attitude orientations. The gearbox includes a plurality of gears that drive various pumps, generators and/or other aircraft systems. A shield surrounds a portion of one of the plurality of gears to prevent lubricant from submerging the gear. The shield defines at least a portion of an open chamber that is at least partially surrounded by lubricant at extreme attitude orientations.