Abstract: A pneumatic system for raising and lowering the landing gear of a trailer, wherein the pneumatic system includes a pneumatic motor totally supported by the landing gear. In this way, mounting of the pneumatic system is independent of trailer type or configuration. A gear shift spline assembly is provided between the speed reducer, that is coupled to the pneumatic motor, and the crank shaft that drives the landing gear's high-low gear reduction assembly. This spline assembly permits the crank shaft to axially translate and shift gear arrangements in the gear reduction assembly without separating the crank shaft from the pneumatic drive.