drive motor a rocker operable by the drive member and translation means operable to move the drive member to a predetermined position on the drive axis application_number US 84323701 A description referring to fig1 and 2 there is shown a drive system generally designated 10 for a vehicle door assembly the drive system 10 comprises a drive actuator in the form of a main motor 12 having a drive shaft 14 extending therefrom a stepper motor 16 having a threaded shaft 18 extending therefrom a drive member 20 slidably mounted on the drive shaft 14 and a yoke 22 mounted on the threaded shaft 18 the drive system 10 further includes a plurality of rockers 24 pivotably mounted to a rocker shaft 26 and a window regulator shaft 28 provided substantially co axially with respect to the drive shaft 14 the rockers 26 are movable to operate door functions such as locking functions via link members 50 the main motor 12 and stepper motor 16 are electric motors the stepper motor 16 threaded shaft 18 and yoke 22 together form a selector actuator as can be seen from fig2 the drive shaft 14 is substantially square in cross section and is received in a correspondingly shaped aperture 30 of the drive member 20 the drive member 20 has the general form of a disc and is provided with abutment surfaces 32 34 adapted to in use engage an engagement portion 36 of respective rockers 24 in the embodiment shown the abutment surfaces 32 34 are defined at opposing sides of.