I have 1100 miles on my 2011 GT (stock 18"s) and I am getting vibration at 80mph+ it is worse when going around turns on the highway at 80+ or when changing lanes at 80+.

The dealer will not test drive the car over the speed limit (65) and at 65 it is smooth.

What should I do?

 

A couple things I would check is.... Go to the dealer make sure the tires are balanced correctly? sometimes the weight falls off rim.Also have you bumped a curb or hit a pot hole recently?your car might need a new front end Alignment?Last thing you might have, a slow leak in one of your tires? check and make sure all tire pressures are up where they need to be..I hope this helped u ..... good luck
{ Please don't forget to vote for Foxbody ROTM for August (click below) }
https://mustangforums.com/forum/ride...ml#post7152616

 

it's most likely that your tires need to be balanced...i had the same problem not too long ago...steering wheel would shake, and it shook under my seat also...took it to the ealer, he suggested i needed my tires balance, got on the highway, did 90, shaking was gone

 

I'm not sure about the 2011's having the same driveshaft as the 05-10 but it may be your clunky driveshaft...

 

While doing 80mph next time, put the car in neutral and see if it does the same thing...
If it's the case, it is whee/brakes related.

I bank on unbalanced front wheels on a car that new...

 

Swapped back wheels to front today and there is still some vibration over 80 mph

 

Do you have the security package? One guy on the Mustang Source forum said he removed the locking lug nut and it got rid of the vibration. Apparently it weighs a bit more than the standard lug nuts.

I would guess your wheel needs to be balanced though.

 

When you say some that mean that there was a change in vibration?? Then your problem is in one of the wheels.

 

That makes sense but I don't think its that much of a weight differential to throw your wheels off balance especially since its in the middle of the wheel.

 

second the tire balance theory