Abstract
This paper shows some results obtained by simultaneous modal analysis of the power unit structure and of the frame structure on which the power unit is mounted. The purpose of this modal analysis is to determine the ideal zones to put the mounts. There are presented the main eigenmodes and some observation about the system behaviour. The analysis concerns two different kind of power units: a longitudinal power unit mounted on a body overhang and a transversal power unit mounted on a rectangular subframe.