A seal carrier that is used to transmit hydraulic fluid to control pistons in a transmission includes a center passage and connecting passages to one or more oil passages. As the seal carrier rotates during operation, the seal carrier acts as a centrifuge and entrapped air in the hydraulic fluid is separated from the hydraulic fluid. The released air moves into the center passage and out through one of the connecting passages, ultimately to a tank or reservoir. A poppet valve in the hydraulic fluid drain rail maintains a positive pressure on the hydraulic fluid at all times to create a pressure differential between the central passage and the tank.