A gearbox includes an inlet configured to receive a mixture of air and oil from an external source and a deoiler. The deoiler includes a shaft including an inlet passage and an outlet passage, both formed on an inner portion of the shaft and separated from one another, a separator unit coupled to and surrounding a portion of the shaft and including an inlet and an outlet and a pre-pressuring component coupled to the shaft that increases the pressure of the mixture of oil and air to form a pressurized mixture and provides the pressurized mixture to the inlet of the separator unit.