an integrated hydrostatic transaxle having a common housing for a hydrostatic transmission and a pair of oppositely - extending differentially - connected axles to have the common housing provide a common sump therefor and with a specifically - shaped center section interconnecting the pair of hydraulic displacement units constituting the hydrostatic transmission . the center section is a unitary member separate from the common housing , with the exterior thereof exposed to the common sump . the center section has passages and arcuate ports which are interconnected by certain of said passages and which are located whereby the center section may be cast to minimize any machining required to finish the center section . such casting can result in a porous center section with possible leakage from a passage having high pressure fluid . however , such leakage is not a problem since the leakage would not be through the wall of the common housing but to the common sump within the common housing which is at atmospheric pressure because of the center section being separate from the common housing .