A drive system for a tiltrotor aircraft operable to transition between rotary and non rotary flight modes. The drive system includes an engine to provide rotational energy and a proprotor assembly to receive rotational energy from the engine when the tiltrotor aircraft is in the rotary flight mode. The proprotor assembly is disengaged from the engine in the non rotary flight mode. The drive system includes a proprotor gearbox including one or more gears mechanically interposed between the engine and the proprotor assembly. The proprotor gearbox transfers rotational energy from the engine to the proprotor assembly when the tiltrotor aircraft is in the rotary flight mode. The drive system includes a lubricant operable to reduce friction between the gears and a lubrication management system to affect a temperature of the lubricant to enhance lubrication between the gears in the proprotor gearbox in the rotary flight mode.