I'm posting this for a friend.  He has a 2004 Vette.  New Kuhmo
tires.  Hatchback (if relevant).  Rims balanced.  When he gets to
75-80 mph, he gets a pulsing vibration in the rear section of the
car.  Dealer could not find the problem.  When he's doing 80, he puts
the car in neutral and the vibration is still evident, so this may
mean that it is not transmission related.

Has anyone any experience with this symptom?  Any inputs that help us
to get to the bottom of this mystery will be appreciated.

You'll probably ask whether he had this symptom prior to putting the
new tires on and balancing the rims.  Can't say.  Vehicle was recently
purchased.  New tires were put on immediately.  Pulsing symptom wasn't
noticed until afterwards.

Phoenix, Arizona