The real world is not only described by linear systems. It is rather generally explained by nonlinear structures, which have a richer behaviour with respect to linear ones. This thesis is devoted to better understand the nonlinear features of vibrating mechanical structures involved in automotive subsystems. It starts from a method to discretise a complex system using Lupos, a MATLAB based software because nowadays simulation and numerical analyses are essential for both linear and nonlinear structures. The device in question is the right lever of the LEVIT F173, projected and assembled at Valeo, Santena. Then a deep look at the major distinctions of the two kinds of systems is performed, dealing with theoretical and practical aspects with the use of different approaches including Simulink numerical simulations of SDOF systems.