to me it sounds like something else, something suspension related. I'd check out tie rods, inner and outer, idler arm, pitman arm, etc. Are you sure that the rotor is all the way back and the tire is mounted correctly? Jack the front wheel up and see if there is any play in it. I'd also make sure there isn't any mud on the inside of the rims or on the control arms. It also sounds like you need a service department not a parts changer.
I choosen to be patient with a vibration problem until I can understand it better or until someone else has a similar problem I can learn from or until FORD admits a problem and offers a service protocal.
Mine is mysterious in that it comes and goes with no clear rhyme or reason. It's mostly felt in the steering wheel, which will vibrate back and forth, usually between 50 mph and 70 mph, but will go away after between 1 and 3 miles of driving. It's not every day that it occurs, and the violence of the vibration is sometimes mild and sometimes quite alarming. It's not weather (temp or precip) related that I can tell, but it usually occurs in the morning or after long periods (4-5 hours) of being parked.
I've had the tires and rims checked and rotated (only 5500 miles on this `08 Expy), but no effect. Plus, if it were driveline related, wouldnt it be everpresent rather than come and go?
Have been to dealer twice, but of course they/I cannot reproduce the problem at that time.
My latest "clue" is that when I tow (24' Featherlite with 4500# load) the vibration, when/if it occurs, is more like a forced movement of the steering wheel rather than a vibration... not very clear in my description, I know, but its making me believe it is POWER STEERING related. Perhaps the spooling is fouled, or some valve is sticking, or ? But this dampening effect under tow load, along with the notion that maybe system/fluid temperature may have something to do with it, I'm thinking the steering pump is the culpret.
Any concurance here on my suspicions? Any other thoughts on what it might be?
I would video the wheel shaking. Send ford a certified letter about your complaint. After 3 attempts, go through whatever your states steps are for filing a lemon. Easy to file. When Ford gets that paper work, they usually respond.