The main objective of this paper is to analyse the dynamic behaviour of thin -rimmed/-webbed gears. A hybrid model is presented, which can capture the instant contact conditions between the teeth as well as the global dynamic behaviour of transmissions including the internal displacements and stresses in gear bodies. Finite elements are combined with condensed sub-structures, lumped parameter elements along with mortar-based mesh interfaces to connect non-compatible models. The results show that gear body dynamic displacements and stresses in thin-rimmed/-webbed gears are stationary in the fixed coordinate system attached to the meshing and relatively decoupled from the dynamic mesh forces. From a numerical viewpoint, it is found that numerical convergence on gear body stresses at high speeds requires significant computational times, thus highlighting the interest of lighter hybrid gear models as opposed to full finite element simulations.