Abstract: A hydrostatic transmission design incorporating a unique housing shape and configuration, including a vertical split of the two casing elements, which are shaped to conform to the internal components of the transmission. The center section of the transmission has a unique configuration including a trunnion mounted swash plate, means for mounting the center section to the transmission and a motor output shaft mounted below the pump running surface. The transmission also includes an expansion chamber, preferably secured externally to the sump, having a tube mounted therein to transfer hydraulic fluid between the chamber and the sump.