I had this same problem on a 2012 F150. I took it into the shop approx 9 times for balancing, drive shaft, new wheels, tires, rims, brakes, rotors, etc. Nothing fixed it, they eventually lemon'ed the truck and gave me a new 2013 F150 at no cost (huge pain in the behind but did work out).
Now I am 20k miles into the 2013 and the same problem is developing. I am starting the same process and expect that this is no different than the 2012 problem. I am on the second visit to the dealer...