A continuously variable automotive transmission (10, 30, 110, and 130) uses an orbital drive having an engine input to an orbit shaft (21, 41) orbiting a cluster gear (25, 45) around a control gear (27, 47) and an output gear (26, 46) meshed with the cluster gear on a common axis. Holding the control gear still produces an orbit drive reduction from engine to output; rotating the control gear forward, which can be done with a hydraulic pump (17) and motor (18), diminishes the reduction for higher speed and lower torque; and reversing the control gear reverses the output drive. A pair of clutches (60, 65 and 67, 70) are available for connecting the orbit drive between the engine and the output for a low range and for connecting the engine directly with the output for a direct drive in high range. The transmission is disclosed in four different preferred embodiments, with an underdrive unit which can be used with any of the embodiments to provide a low-low transmission for use in heavy trucks.