Engine mounts(engine seats) is another source of noise in vehicles, from my own experience, a Toyota Corolla had horrible noise from vibrations. It sounded like the gear itself was gnashing it's teeth in a loud anguish filled wail, especially when doing 60kmph and above. It got so bad and convincing that a rupture was going on inside the engine/gear (it's an auto transmission). After a lot of study, it was discovered that the upper engine mount near the alternator assembly was not looking good, it was replaced and Pronto like a magic the vibration and noise vanished.