A cable drive unit for opening and closing a sliding door on a vehicle (not shown) has a cup-shaped front drum having a helical front cable groove and a rear cup-shaped drum having a helical rear cable groove. The front drum is rotated about a longitudinal axis in a first direction to open the sliding door. The rear drum is partially nested in the front drum and rotated about the longitudinal axis in an opposite direction to close the sliding door. The front drum and the rear drum are drivingly connected to each other via a tension spring that biases the front drum and the rear drum in opposite directions when in tension. The front and rear drums are rotated by a concentric clutch that is nested in the rear drum. The clutch includes a drive member that is drivingly connected to the front drum via a first lost motion connection and drivingly connected to the rear drum via a second lost motion connection. The first drum has an arcuate slot forming part of the first lost motion connection, the rear drum has an arcuate slot forming part of the second lost motion connection, and the drive member has a tab that projects through both arcuate slots to form part of the first lost motion connection and part of the second lost motion connection.