Recently, EVs (electric vehicles) are getting popular as the transition to EVs from ICE (Internal Combustion Engine) vehicles is happening in the mobility market. In the NVH perspective, EV’s show better performance than ICE vehicles due to non-reciprocal motion in electric drive units. The drive units in EVs are much simpler than those of ICE vehicles, where the drive unit has a single-speed transmission and an electric motor. Furthermore, EVs have no idle issues nor auto-start issues. However, EVs have unique NVH issues that ICE vehicles do not manifest. These issues are inherent in electric motors: high torque at low speeds, torque reversal for regenerative braking to improve range. Various analysis methods have been developed to predict the NVH characteristics of electric vehicles. One of the most representative methods is the frequency response analysis with sources of excitation. However, this NVH analysis method has been applied mostly to steady state problems in the frequency domain. Regarding EV NVH performance, time transient cases as well as steady state cases should be analyzed to comprehend the natures of electric motors. In this study, a new NVH approach of multi-flexible body dynamics and electro-magnetic motor forces is proposed. The approach incorporates excitation sources at transient geartrain contacts and electromagnetic torque fluctuations from the motor. It gives an advantage in transient time domain analyses, where the motor RPM and torque are changing over time such as regen brake, wide open throttle, and driveaway. It better incorporates the degrees of freedom of the system and the NVH characteristics of the geartrain can be better represented. To demonstrate this approach, a drivetrain model was developed with gears, bearings, shafts, and the motor. The model was built in Ansys Maxwell for electromagnetics and Ansys Motion for the geartrain. The system is subjected to excitations from the geartrain contact forces and the electro-magnetic forces generated in the motor. The operating condition of the drivetrain system is defined for an acceleration case, where the motor speed is accelerated from 0 to 10,000 rpm. On top of the acceleration, the rotor is subjected to a 200Nm torque in the rotor shaft. Acceleration responses were calculated from a few points on the geartrain case. The acceleration outputs give a frequency response of the geartrain, which are further processed to identify contributions to the overall NVH performance from each vibration source: gear whine, gear rattle, gear design variations, and electromagnetic forces. This workflow can be applied to various EV drive unit systems in time transient scenarios. Also, it can be applied in the drivetrain design process, where potential problems can be identified and brought into discussion early in the development process. It will also help to provide balanced designs between drivetrains and vehicle systems. One of future study topics would be an application of this approach to acoustic analysis for electric drive units.