Due to their power density, recirculating-ball power steering systems with hydraulic support are installed in commercial vehicles. To simulate the loads necessary for designing the steering system, a model of the overall system comprising the dynamic vehicle and steering system is needed. In this paper, a hydraulic recirculating-ball power steering system is modeled with SimulationX and, using the FMI, coupled with a SIMPACK vehicle model to create a simulation of the overall vehicle. This integrated simulation enables to analyze, for example, the influence of hydraulic components and parameters (valve characteristic, oil feed, hoses) on the overall vehicle behavior.