The invention relates to an evacuated transmission case. The vehicle transmission includes at least one rotatable component and is disposed in an environment at a first pressure. A transmission housing includes a sump portion disposed near a bottom portion of the transmission housing, where the transmission housing substantially encloses the at least one rotatable component. A hydraulic fluid is disposed at least partially in the sump portion of the transmission housing and a vacuum source is in pneumatic communication with the transmission housing. The vacuum source at least partially evacuates a gas from the transmission housing so that an interior of the transmission housing is at a second pressure. The at least one rotatable component is partially exposed to a gas at the second pressure and partially submerged in the hydraulic fluid when the transmission is under a predetermined dynamic load.