i have a 2011, 5.0 with 35000 miles on it. started to notice shaking in the seat a month or so ago, thought it was the tires out of balance. since they were just about bald i thought it time for new ones, got brand new tires professionally installed and balanced. shaking is still persisting, i have also checked the U joints for any play and seem to be solid. the shaking is happening at all speeds, not like a death wobble or anything really bad just small but constant vibrations. Suggestions on what this could be? thanks!

 

It sounds to me like it's in the drive line.

Unk Bob

 

Mine is doing the same thing, and Ford can't fix it or will not. I have had new tires, road force balance, new drive shaft, and it still vibrates around 55mph up to 75 or so.
There are a lot of post on vibrations, so do a search.