I just came back from the dealership where they gave me two new front tires and balanced them because the old two were cupped and causing the steering wheel to shake at 60-70mph...

Now with that fixed, on my drive home i got to about 80mph to pass someone on the highway and as soon as i hit that speed I hear this loud humming noise and it feels like its under my seat or in the back area. I can definetely hear and feel it quite well.. It gets worse as I push the speed up a bit more to test it... Could this be a drive shaft problem?

They said my alignment was fine all around since they had to hook it up to check the front already.... Any ideas?

 

Did they do anything to the rear tires? Align? Balance? anything? If they just aligned your rears after driving for a while on the tires, the tires could be cupped or worn unevenly and now that they are straight, you're hearing the bad tires.

 

Ok no they did not do anything with the rears at all. They put entirely new fronts balanced on and that solved the steering wheel shake... When they checked the alignment they had to hook up all the tires and said the alignment was fine.. I took it that the entire alignment was fine and didn't specify the back because i was not having this problem. I assumed if there was a problem with the back they would say something, because the machine having used a newer 'hunter' myself checks all corners and requires all 4 tires hooked up to even do just the front.

However since owning the car for only a month, and it had the front tire problem I was hesitant to fast with it and took it easy till my new front tires were on. Now that they are on, i figured i would push it a bit, and i get this really weird feels like drive line vibration at 140km/hr. I can't actually hear a howl but more of a hum and it feels like your driving on the shoulder of the highway with those warning strips almost but not quite as bad.