2003 front end problems?

OK so I recently bought a 2003 LS8 and I LOVE IT! It was smooth as a babies butt at 100mph. It has about 43,000 miles on it.

About 2 weeks ago I started noticing what felt like grinding in the front end. I could feel it in my feet through the pedals. Next I felt some shaking in the steering wheel at around 70-80 mph. I do not know if the 2 are related. Anyway I brought it to the dealer and had the tires rotated and balanced. It did not make a difference. It is still shakey at the same speeds. The problem I am having with the dealer is they refuse to test drive it at those speeds. They said I can not ask them to break the law in order to test drive the car, and at 65 it feels great. I was wondering if anyone has any ideas?

I have heard that the LS8 is famous for front end troubles. If you can give me some ammo to go to the dealer with it would be appreciated.

Did the dealership check the front end for any loose components? I would hope so if you told them about the problem rather than just asking them to rotate and balance the tires.

The common front end problems were on the 1st generation LS if I recall correctly, so your 2003 should not have the problem components.

-Rod