Vibrate on highway

Hi, there

I have a Sienna Toyota van (Year 2000). It was all fine and ran well on freeway. A couple of months ago, I got grinding noise when I apply the brake. So I took it to a mechanics shop, “Firestone Complete Auto Care Store”. They found quite a few problems with the brake system. As a result, the rotors, drums, brake pads, braks shoes and calipers are all replaced. After that service, whenever I drive the van on freeway, I got bad vibration whenever I drove it to about 65 MPH. I took it back to the same shop. They did alignment, balance and rotate the tires. Still, I got the same bad vibration. Last weekends, following the shop’s suggestion, I had them replaced all four tires. Well, after that, I still got the same bad vibration. Seems to be the shop ran out of ideas.



What it could be wrong?



Thank you very much.



Xuelong