My 2003 G35 Sedan has increasing noise from the drivetrain.
it is noticeable around 40 mph and increases as speed increases.
the sound is more of a "whine" than anything else, similar to the engine rpms if highly revved, but the tach relates normal rpms. we have changed tires, put car on rack to see if running it created same noise (not), put car in neutral going down the road (no change in noise).
we went to infiniti dealer this week, they had two technicians look/drive it, and think it is transmission not shifting out of 3d - but the tach does not show high rpms....