Driveline (DL) is one of the major sources of noise and vibration which excites the vehicle structures across a wide band of frequencies in commercial vehicles (CV). Current work focuses on the driveline noise source identification and its reduction in a heavy commercial vehicle. An abnormal noise is perceived in a CV in high gears at high speeds. This annoying DL noise is subjectively perceived in geared and neutral coast down conditions. Objective NVH assessment including near source noise and vibration of the driveline components was performed to quantify the noise. Initial test results revealed that the DL excitations are aggravated in auxiliary gear box as broadband rattle noise. The design configuration of the DL components and related subsystems such as propeller shafts and gearbox etc. was studied to the find root cause of the excitations. The driveline configuration including the auxiliary gearbox tooth geometry is also scrutinized and modified. It is observed that the intensity of abnormal noise during geared and neutral coast down is reduced with modified auxiliary gearbox. Also, propeller shaft balancing, positioning and alignment improvements proved betterment in noise and vibration results.