With a view to simplifying the simulation models and shortening the computation periods, the author extends the building block approach (BBA), which is commonly applied to linear analysis with the finite element method, to non- linear areas, and applies the extended BBA to drivetrains.When the frequency of the vibration being studied is more or less known, the restrictions of the conventional vibration mode selection method are shown to be significantly relaxed by the modal compensated method described in this paper. Further, when the BBA is applied to time-response analysis and the effect of a decrease in freedom and the time-step-expansion effect of the removal of high- order components are analyzed, the effect of removal of high-order components is shown to be particularly great. Also, an increase in the intensity of nonlinearity necessitates a smaller time step with the conventional method, whereas the time step with the BBA is hardly affected by the intensity of nonlinearity. The effect is that the higher the intensity of nonlinearity, the greater the BBA-enabled reduction in computation period, With a light-load drive condition, the computation period is reduced to one-thirtieth of the original period.The main cause of noise under a light-load drive condition is assumed to be impact hitting of the second- and first-stage of clutch disc. An example of the elimination of impact hitting and related noise using multi-stage torsional characteristics is given in this paper. Also, the effect of the clutch discs'' multi-stage torsional characteristics on drivetrain noise under a heavy-load drive condition is described.