The paper presents the sources, the propagation paths, the vibration mode behaviors and thenoise radiation properties that control thenoise radiation in the front side ofadieseltruckengine. Measurements and analyses of vibrations and radiated noise have revealed that the overall noisefromtheengine front radiates fromthetimingtransmission casing, the oil sump front and the belt pulley/torsion damper arrangement. Thetransmissioncoveronthe investigated engine is coupled directly to the oil sump front and it is manufactured in cast aluminum. Thecover and the oil sump front show strong coupled modes that are dominant radiators ofnoise in the frequency range 630 Hz - 1 kHz. Thenoisefromthetransmissioncover has been reduced by replacing the interior plate ofthecover with plastic plates that have decreased radiation efficiency and increases damping. The radiation fromthe narrow opening between the torsion damper and thetransmissioncover was found to be an important radiator and to be caused both by thecover and the damper. A damping ring covering the opening was found to produce substantial reductions ofnoise.