A self-propelled snowthrower wherein, in one embodiment, drive members on each side of the snowthrower provide variable speed propulsion. A transmission that delivers power to the drive members may be adapted to de-clutch one of the two drive wheels when the ground speed of that wheel exceeds the driving speed of the transmission. In other embodiments, the snowthrower includes a rotor having a snow ejection surface forming a negative rake angle. Yet other embodiments include a chute rotation control mechanism that permits manual discharge chute rotation via one-handed input.