As environmental concerns have taken the spotlight, electrified powertrains are rapidly being integrated into vehicles across various brands, boosting their market share. With the increasing adoption of electric vehicles, market demands are growing, and competition is intensifying. This trend has led to stricter standards for noise and vibration as well. To meet these requirements, it is necessary to not only address the inherent noise and vibration sources in electric powertrains, primarily from motors and gearboxes, but also to analyze the impact of the spline power transmission structure on system vibration and noise. Especially crucial is the consideration of manufacturing discrepancies, such as pitch errors in splines, which various studies have highlighted as contributors to noise and vibration in electric powertrains. This paper focuses on comparing and analyzing the influence of spline pitch errors on two layout configurations of motor and gearbox spline coupling structures. The first involves an integrated approach where the motor shaft and gearbox input shaft are combined and share a single shaft, while the input gear is attached using splines. The second approach features a separated configuration where the motor and gearbox exist as separate entities and are connected by splines. Through this analysis, the study investigated the impact of pitch errors occurring in the splines on dynamic behavior. To ensure early NVH performance in powertrain development, the study utilized both quasi-static software RomaxDT(is software B) and multibody dynamics software ADAMS(is software A). Although both layouts are susceptible to vibration caused by pitch errors in the splines, the mechanisms were found to be different. This research has established a process for understanding how the coupling of the motor shaft and gearbox input shaft affects system behavior and NVH performance. Additionally, it underscored the importance of managing spline pitch errors in the layout of motors and gearboxes.