An automatic transmission assembly for mounting to a power-source includes a torque converter operatively connected to the power-source. The transmission assembly also includes a turbine shaft for receiving power-source torque from the torque converter. The transmission assembly additionally includes a torque transfer system, having a gear-train and a hydraulic pressure operated torque-transmitting device, for receiving the torque from the turbine shaft and selecting an input-to-output speed-ratio of the transmission. The transmission assembly also includes an output member for receiving torque from torque transfer system and outputting the torque to drive a load. The turbine shaft defines a first passage configured to supply hydraulic pressure to the torque-transmitting device and a second passage configured to vent to atmosphere. The turbine shaft additionally defines a third passage fluidly connecting the first passage to the second passage and thereby configured to bleed air from the torque-transmitting device.