A power transfer apparatus including a clutch having a biasing device for biasing the clutch piston in a direction in which the clutch discs engage with the clutch plates, a transmission brake disposed in line in an axial direction of the clutch, an actuator disposed in line in an axial direction of the transmission brake for disengaging the clutch at the same time of applying the transmission brake, and a planetary carrier sub-assembly disposed in line in the axial direction of the clutch, wherein the power transfer apparatus provided between an input shaft and an output shaft which are accommodated within a casing for selectively changing the speed of the output shaft.