A wheelchair which shifts between forward and reverse by virtue of a roller mechanism which grabs in one direction and slips an opposite direction, thereby preventing binding. The shift mechanism is initiated by rotation of a shift paddle which is located on a extremity of a lever arm remote from the roller mechanism.

A crank including a mechanism capable of connecting the crank arm to a shaft to drive the shaft in rotation in either a unidirectional drive mode or a bidirectionally driving mode, the mechanism being quickly adjustable between modes. A coupler in the mechanism may be slidable between a first position engaging the crank arm with a hub portion fixedly mounted on the shaft and a second position in which a unidirectional clutch can operate to allow rotation of the crank arm freely about the shaft in one direction but cause rotation of the shaft in the opposition direction. The coupler may be arranged to be coupled only when the shaft is in a selected angular position.

A wheelchair includes a standard foldable frame for supporting a seat with a first and second drive wheel driven by drive levers. Each wheel has a transmission providing for three forward speeds and a reverse speed, as well as a neutral position. The transmissions for the two wheels may be constructed of identical parts with the wheels being caused to rotate in opposite directions from the driving lever merely by reversing the direction of the pawls within the transmissions. The ratchet drive surfaces are provided with pawl engaging surfaces which may be driven in either of two directions. The wheelchair does not require any bulky equipment and the hub containing the transmission may be the size of a bicycle hub. The transmissions in both wheels are shifted by a single control. The wheelchair is provided with disk brakes.