A sliding door drive assembly is provided for a vehicle. The assembly includes at least one grooveless drum. The drum has a cable wrap surface and is rotatable to wind cable thereon and unwind cable therefrom. A guide is positioned to be aligned generally with a first axial edge of the cable wrap surface. As cable is wrapped on the drum, the angle of the cable (due to the position of the guide) biases the cable towards the first axial edge, so that successive wraps of cable are snuggly positioned adjacent prior wraps. In another aspect, a cable drum includes a ramp at a second axial edge of the cable wrap surface, which guides the cable radially outwardly to start a second layer of wraps of cable on the first layer of wraps. In another aspect, an absolute position sensor is provided for a powered sliding door.