Abstract: A hydrostatic differential transmission comprising a cylinder housing containing an input pump and an output pump. The two hydraulic pumps are mounted with the output pump inside the input pump. The input pump has an adjustable swash plate. The output pump has a fixed swash plate. The pistons of the input and output pumps share inter-connected piston bore housings. An adjustable control selectively pivots the adjustable swash plate between a neutral position, where the swash plate is at a 90 degree angle to the input shaft and maximum tilt of the swash plate for a one-to-one ratio of the input shaft and output shaft.

Abstract: A hydrostatic differential transmission includes a pair of cylinder housings (58, 62) rotatably mounted for free rotation on coaxial input and output shafts, respectively, with a first pivotable swash plate (101) and second fixed swash plate (24b) fixed to the input and output shafts, respectively and a differential. An adjustable control selectively pivots the first swash plate between a neutral position, where the swash plate is at an angle to the input shaft equal to the angle of the second swash plate to the output shaft, and a direct drive position, where the swash plate is perpendicular to the input shaft. The differential includes a forward ring gear (32) fixed to the input shaft, a rearward ring gear (30) fixed to the output shaft and pinion gears (38, 40) between the forward and rearward ring gears. The pair of cylinder housings rotate together (via 36, 96) and have the pinion gears rotatably mounted thereto, for driving an auxiliary pump (48).

Abstract: A hydraulic transmission operates throughout a continuous range between a neutral condition and a direct drive one to one ratio of input shaft speed to output shaft speed. The input shaft carries a rotor which provides a hydraulic pump for the input side of the transmission. Reciprocating pistons of the input pump move in camming fashion against an input side swash plate as the input shaft rotates. The fluid that is displaced in the input side pump is directed into an output side pump which is carried on the output shaft. Reciprocating pistons of the output pump are hydraulically forced against an output side swash plate to effect rotation of the output shaft. A sleeve and lever assembly controls the stroke length of the pistons of the input pump in order to vary its fluid displacement relative to that of the output pump, thereby varying the transmission ratio.