This paper addresses the problem of autonomous control of a hydraulically actuated articulated-frame-steering (AFS) mobile machine- a wheel loader. Our autonomous motion control system includes a mission planning graphical user interface, an improved odometry algorithm and a GPS device for navigation purposes, together with a model based path-following control strategy, and speed control. The test platform is a small prototype wheel loader based on Avant-635 whose hydraulic components are substituted by electrically controlled equivalents. System development and preliminary calibrations are done using GIMsim- an elaborated semi-empirical hardware-in-the-loop simulator. Some field experiments are presented that demonstrate satisfactory performance of the system at this stage. Further tunings are required to reach a desired performance.