Abstract: A tracked-vehicle drive has a wheel rotatably driven about an axis and having an outer surface, an endless traction element spanned over and frictionally engaging the wheel so as to be advanced thereby when the wheel rotates and having an inner face formed with an endless row of spaced teeth, and an auxiliary drive member displaceable adjacent the traction element and formed with an endless row of spaced entrainment formations in constant mesh with the teeth so that the drive member is displaced synchronously with the traction element. A coupling body having entrainment formations in constant mesh with the drive-member entrainment formations is engageable with the wheel outer surface. The body can be coupled to the wheel for positive driving of the traction element from the wheel via the member and body and can be decoupled from the wheel for frictional coupling of the traction element by the wheel.