For the last year or so, my van has had a really bad vibration that occurs at roughly 70mph +. It's not always there though, and sometimes is gone for many highway miles, but then rages back with a vengeance to the point that the whole vehicle shakes, not just the steering wheel (but the wheel shakes badly also). When it started, I had a pretty worn set of tires, but still balanced. Recently I had 4 new Nokian enTyre 2.0s put on, and balanced of course. Problem didn't get any better or worse. I then had a front control arm ball joint fail, so I replaced 2 front control arms, also replaced the sway bar links in front for good measure, and got an alignment. This fixed a clunk I had but the intermittent vibration is still there. Rotating wheels makes no difference. What could this be? Recently it seems that one of the strut bearings makes an intermittent noise when turning, but could this cause a vibration? The front struts are original, FWIW. Any ideas would be very much appreciated. The place I take the van to for alignment work is pretty keen on finding bad parts and will generally refuse alignment if bad parts are found, and they didn't find any last time.