Considering the practical problems of gear noise and vibration, this work focuses on the gearbox of the electric vehicle as the research object to analyse the impact of gear micro-tooth modification. First of all, the effort centres itself on minimising the contact stress and making the load distribution better by implementing the tooth modification on both upper and central speed phases. The procedural analysis of gear tooth modification is executed to make the contact pattern better, so edge contact has been avoided and the load is distributed over a wide area of the tooth for both upper and central gear sets. The contact pattern is positioned in the centre of teeth and contact stress is lowered by 20% to 837 MPA. Then, the peak to peak transmission error is decreased under three proposed modification approaches. Also, contact and bending safety factors are improved as a result of tooth modification. Meanwhile, it was noticed by performing dynamic analysis that right bearings of both upper and central phases have a higher radial response for first two orders which is further decreased to an optimum level as a result of micro-tooth modification strategies.