A motorized wheelchair rear wheel drive assembly is selectively engageable and disengageable by an occupant to permit the wheelchair to be used in either a motorized mode or an occupant self propelled mode. For each rear wheel a drive motor connects through an axially extending worm gear assembly and rear drive axle to a drive hub. The drive hub is positioned outside of the rear wheel and supports a control handle which in turn controls a pair of locking pins which selectively engage the drive hub or disengage the drive hub from the rear wheel. The drive assembly enables the wheelchair to be folded to a laterally more compact condition.
