A power operating system for opening and closing a vehicle liftgate has a pair of drive units supported on the vehicle frame and connected to the liftgate for opening and closing the liftgate. Each drive unit includes a bracket that is secured to the vehicle body for supporting several parts including a reversible electric motor, a gear train, a rack and a cradle that are mounted on the bracket. The electric motor drives the rack via an the output gear of the gear train that has an axis. The rack slides in the cradle which is pivotally mounted on bracket so that cradle pivots about the axis of the output gear to hold the teeth of the rack in engagement with the teeth of the output gear to accommodate rocking movement of rack as it moves from a retracted position to an extended position. An arcuate track that is fixed to the vehicle body, and an arcuate link slides in the arcuate track. The arcuate link has an inboard end that is pivotally connected to an end of the rack and an outboard end that is pivotally connected to the liftgate.