A drive device includes a housing forming a sump. A pump and motor are mounted on a center section having a porting system and a pair of ports with check plugs disposed therein. A bypass arm is engaged to one end of a bypass shaft external to the housing and rotates the bypass shaft to selectively cause engagement fingers to move each check plug to an open position. A housing projection is contacted by the bypass arm to selectively limit rotation thereof. The axes of rotation of a swash plate trunnion shaft, a pump input shaft and a motor output shaft may all be disposed in a single plane. The input shaft is supported by a housing bearing and an opening in the center section and is restrained from axial movement by the bearing and a thrust surface on the center section.