Generally, a method of a hysteresis loop is used to show the property of the clutch system in the design process. This represents the load by a pedal travel which is a useful data for designing a vehicle for the comfort of the driver. Transfer torque of manual shift gear types for heavy duty vehicles is too high. Therefore unlike passenger car air pressure is added to the clutch system in addition to the fluid pressure. In this case it is hard to predict nonlinear element to control the hysteresis because of the addition of the components. In this paper theoretical model of the system components involving variables such as mass, stiffness and damping is developed and simulated. The results of the actual test of the clutch system are compared with simulation.