Abstract: A vehicle transmission unit is housed in a casing and includes a plurality of drive ratio paths selectively engageable by a ratio selection system. The ratio selection system includes fluid-pressure-operated actuators under the control of solenoid-operated valves to select the operative drive ratio of the transmission. The transmission also includes one or more mechanical actuator members accessible from outside the casing which can be manipulated to select one or more drive ratios of the unit in the event of the failure of the fluid-pressure-operated actuators or valves.

Abstract: A continuously variable transmission includes an input shaft, an output shaft, and first and second epicyclic gear trains, each with an input member, an output member and a reaction member. An hydrostatic shunt loop including first and second hydraulically interconnected variable displacement hydraulic units interconnects the two epicyclic gear trains. The input members of both epicyclic gear trains are driven from the input shaft, and the output members of both epicyclic gear trains drive the output shaft. First and second drive trains are provided for alternatively coupling the first variable displacement hydraulic unit respectively to either the input shaft or the reaction member of the first epicyclic gear train. Third and fourth drive trains are provided for alternatively coupling the second variable displacement hydraulic unit respectively to either the output shaft or the reaction member of the second epicyclic gear train.

Abstract: A gear unit provides a number of operative ratios engaged by fluid pressure operated clutches operated by clutch actuators. These actuators are controlled by two-position flow reversing valves, one valve for each fluid pressure operated actuator. These valves are hydraulically connected in series with at least one actuator connected downstream of the last valve in the series connection and at least one actuator connected between each valve of the series. A valve control means is provided for controlling the operating sequence of the valves so that by changing the operative condition of one valve at a time the operative ratio of the gear unit can be changed to the next adjacent ratio provided by the unit in a progressive manner throughout the entire ratio range of the unit.