Hi Scotty,
How r you doing. I have a question about car shaking or vibration problem on highway. I have this 2013 lincoln mks 3.7 liter. I Have problem of vibration on highway speed 50 and above could be also at lower speed but hard to notice. It's been two year since had this problem but no mechanic is able to find. Changed inner and outer tie rods changed sway bar bushings changed front shocks changed engine and transmission mounts. Changed one of the axle two years ago and front wheel bearings. Balancing and alignment done. But the vibration is still there. Should I drive it you for checking.
Thank you.

start with a high quality alignment shop, there are many bozos out there. i use cotton brothers in houston and they always figure such stuff out. Years of experience trump everything and your problem will require that, rather than guessing like people have been doing so far