Reduced order modelling is of crucial importance for the dynamics of complex Finite Element structures. Thereby the overall deformation state is approximated by a superposition of weighted trial vectors, commonly called modes. The weighting factors (‘modal coordinates’) are obtained by numerical time integration of the reduced order model. In case of complex systems, the time integration normally dominates the overall simulation time. A multibody simulation of a flexible crankshaft interacting with pistons, con rods, fly wheel, hydrodynamic bearings and furthers for instance, takes at least several hours of CPU time. The modal coordinates can then be used for modal stress recovery in order to predict the fatigue lifetime. If a variant of the flexible body with small changes needs to be investigated, a new numerical time integration is necessary. In this paper a method is proposed where the modal coordinates of a flexible body will be projected unto another mode base. This will be done by using the key idea of the SEREP method where the modal coordinates are computed via the Pseudo-Inverse. One academic and one industrial example demonstrate that the time integration of the variant can totally be skipped without remarkable loss of accuracy, as long as the differences between the two flexible bodies are small enough.