[psiperformance]

yes
because the factory drive shaft actualy has harmonic damping material inside it.. it also has cv joints instead of u joints wich give a cusion to the tranmisssion in how it conects to the rear and transmit less vibration ..

its not that the drive shaft vibrates more its just that by its design it transmits more of the vibration that is there though the drive train.

same thing i tell people when they put in large gears .. expect a slight increase in nvh because everything in the rear end is spinning so much faster.

for example you go from 3.27 to a 4.10 gear well now at 70 mph your drive train is spining as if you were going 90+ so you have to expect more vibration just fomr the bearings doing their job..

nothing crazy of course but it is noticeable epecialy in the new mustangs with the ultra smooth cv joint shafts etc.