A vascular imaging system with an automated longitudinal position translator includes a drive unit with a single motor to provide for rotational and longitudinal translation of a drive-cable and distally mounted transducer within a catheter assembly. The drive unit includes a main body casing and a pullback carriage on which the main body casing slidingly engages. The drive-cable is mechanically coupled to the motor, and an outer sheath of the catheter assembly is fixed to the pullback carriage via a rigid pullback arm. The imaging system can be made to operate in an automated longitudinal translation mode, wherein the main body casing of the drive unit is made to uniformly and longitudinally move relative to the pullback carriage by the drive unit motor, thus causing coincident longitudinal movement of the drive-cable (and distally located transducer) relative to the outer guide sheath of the catheter assembly.