Vehicle liftgate power operating system

A power operating system for opening and closing a vehicle liftgate has a pair of drive units supported on the vehicle roof 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 unit and a housing having a forward linear track and a contiguous rearward curved track. The electric motor drives a segmented drive linkage disposed in the housing via the gear unit. The segmented drive linkage includes an elongated arcuate link that is guided by the rearward curved track, a linear rack link that is guided by the forward linear track, and an intermediate link that has an outer end that is pivotally attached to an inner end of the arcuate link and an inner end that is pivotally attached to a midpoint of the linear rack link. The outboard end of the arcuate link is pivotally connected to the liftgate to open and close the liftgate as the arcuate link is extended and retracted by the linear rack link being driven by the electric motor.