The paper presents a HiL test setup for hydraulic propel systems that includes a multi-body dynamic simulation of a vehicle in a realistic 3D environment. It allows testing of driving scenarios under load conditions that would otherwise be very difficult to obtain. The hydraulic-mechanical part of the simulation is modeled in Simulink. An open-source C++ physics engine is used to model the vehicle multi-body mechanics and collision detection between the vehicle and the 3D environment. Despite the high complexity of the hydraulic drive train component models, the constraint of real-time execution of the simulation on a real-time target can be fulfilled.