I. ABSTRACTThe suspension of the power train unit has a very substantial effect upon the vehicle's comfort in terms of noise and vibration.As it plays a rather complicated role and as the functions that are to be fulfilled are often conflicting, the designer is continuously searching for the best compromise.The suspension of the power train unit must: position the engine in relation to the nearby structure and components, and within a usually restricted suspension travel. convey to the structure the stresses from the engine's weight and torque, while filtering and absorbing. the vibrations linked to the thermodynamic cycle and to the inertias of reciprocation masses. This vibration is within the 30 to 200 Hz frequency band, and is transmitted by solid means to the structure and intensifies the “humming sound” inside the passenger compratment. the medium-wave vibration generated by the transmitted motions (squealing of gears and belts). 100 to 600 Hz frequency range. low frequency vibration engine idle vibration - 20 to 30 Hz. torque pick-up when accelerating and decelerating the power train unit's specific mass on its supports - 8 to 15 Hz.