i had heard they had a recall on some Passions because the roof or windshield would COME OFF.
one of our "Indiana Smarties" had this happen to HIS Passion. it was a problem with the paint not adhering to the Tridion Cell and the windshield and Panorama roof are glued to the paint. the paint comes loose and then so does the windshield or roof.
the 'fix' is to remove both and repaint the area and then reinstall them. hope this is what your smart center did to correct your 'vibration'.
loosing a roof or windshield at highway speed could be quite an experience!!