This paper gives a general framework which allows to couple non-matching sub domains in large displacements and rotations for transient non-linear analysis. The coupling of non-matching subdomains has already been published previously, and we focus, in this paper, on the interest of using modal subdomains in some analysis, give a 4-mass formulation for large rigid body modes but small strains. The efficiency of the method is compared to usual 3D impact analysis. It is shown that the method can lead to 30 or more CPU cost reduction.