I have a 2005 F150 STX 4.6L it had a shake in the what feels like the driver front tire. With old tires but was due for new tires had them installed thinking that it would cure problem ( tire out of balance maybe). Noticed that shaking is still there from 50 - 55 not really a bad shake mainly just worry some. Got under truck did not see or feel anything loose or out of place. Have not tried to jack truck up to see if ahy wobble in tire yet any ideas it has only 22,000 miles on it

 

I'd take it to the tire shop and tell them what it's doing. They should be able to see what it is.

 

Does the steering wheel wobble? If so I'd say it was most likely the front wheels. If not I'd check the rear wheels as well.

It also could be the parking brake. If you don't use the parking brake regularly it tends to rust and then when you finally do use it, it gets stuck partially engaged. This then causes the rear wheels to shake. You can check to see if this is the problem by driving down the road for a couple miles with the truck shaking. Then stop and feel the rear wheels and tires to see if they are warm and if you can smell the brakes. If you cant then it's most likely a wheel balance problem.