This work presents NVH performance improvement of a gear transmission system for an electric vehicle. This system consists of two stages of helical gear pairs with the first-stage output gear and second-stage input gear on one shaft. A vehicle NVH test revealed two major noise issues in the first mesh frequency harmonic of the first-stage gear pair. The first problem was a resonance at around 7850 rpm of the motor speed with the resonant frequency of 3533 Hz. Modal tests with LMS TestLab showed that 2 nodal diameter (i.e., Fourier) component of the first-stage output gear axial vibrations dominates the resonant modes. Modal calculation with a finite element software was consistent with the modal test result. Changing the gear web of the first-stage output gear with ten cylindrical holes to one with four non-cylindrical holes shifted the natural frequency of the 2 nodal diameter modes out of the operating speed range with around 20% of weight increase. The second problem was that noise amplitudes near the motor speed 4700 rpm at the maximum motor torque were around 7 dB higher than the required limit 35 dB. This large noise correlated to the large peak-to-peak transmission error at the maximum motor torque. Tooth micro-geometry optimization significantly reduced the peak-to-peak transmission error at the maximum motor torque from 0.34 \(\mu \) m to 0.08 \(\mu \) m. The above improvements reduced the noise near the motor speed 7850 rpm by more than 16 dB and that near 4700 rpm by around 10 dB.