Sensing the load dynamic in an overhead crane is not a simple task because both load angular position and velocity measurements are not easily attainable and subject to disturbances. A method to reconstruct the dynamic of the load is presented. It is based on the estimate of the torque that the load produces on the drive that governs the translational dynamic of the trolley at which the load is hanging. It requires a minimal sensor equipment, namely measures of the electrical torque and angular velocity of the drive, as both swing angle and load speed are shown to be observable for the linearized model.