The method discussed is how torque-speed data given at the input or output coupling of a drive system can be converted into a specific load spectrum for the rating of every gear mesh, bearing, and shaft of the system. The procedure differs for these elements, depending on how the load is operating. A gear tooth is submitted to a pulsating load, so, if the torque never becomes negative, no alternating stress happens. A ball of a bearing always gets a pulsating load, regardless of positive or negative torques. A rotating shaft is always submitted to alternating bending stress, but torsional stress amplitudes normally are small when the torque varies slowly (compared to the rotational speed), so often torsional stress is less damaging. Therefore, the conversion of time series data into a load spectrum is done with different methods for gears, bearings, and shafts; furthermore, the method must be adapted if the torque is changing from positive to negative.  In the second part of the paper, the method of verification with load spectrums for shaft and bearings is explained. These methods are not yet covered by ISO standards, so the verification of bearings is according to literature and the verification of shafts is according to FKM documentation.