Abstract: A planetary gear assembly comprises, a housing with an input shaft rotatably mounted in the housing and being advantageously hollow so as to provide a means for rotatably supporting a central gear. The central gear includes two axially spaced helical gear portions which mesh with oppositely helically geared rotatable planetary gears having respective shafts supported on planet carriers which are selectively connected either to the input shaft or to an output shaft which is rotatably mounted adjacent the input shaft. A planetary gear is also meshed with outer central gears or internal gears which are affixed to the housing. The inner central gears are mounted so that they may be displaced axially to absorb stressing during operation. In addition, the internal gear advantageously includes a hub portion which provides a mounting for a planetary gearing of another faster running planetary stage.