The methodology of modelling and of qualitative analysis of large rotating systems with gear and bearing couplings is presented. The emphasis is laid on the modelling of nonlinear gear and bearing couplings and on their influence on the dynamic system response to the internal kinematic excitation in gearing and to parametric excitation caused by the time-varying meshing stiffness. The aim is to introduce a method of investigation the beahviour of the rotating system influenced by the mentioned excitation and to examine the influence of chosen operational parameters. The methodology of modelling and of qualitative dynamic behaviour analysis is tested on a two-stage gearbox. and Obsahuje seznam literatury