I have a 1990 F150 XLT....its in great shape but it recently started to shake a bit when I am on the highway...it is fine on back roads at lower speed. When I grab the front right tire (while on the ground) there is a very slight bit of play. Does this mean the wheel bearings are bad if the lug nuts are tight?

 

What I would do is jack each front tire off the ground. Then hold the tire at 12 and 6, and see if you can make it move and find looseness. If you can, then look at the ball joints while moving it to see if the play is in the ball joints. If so, you need new joints. If not, most likely either your wheel bearings are loose or they need to be replaced.

 

Looseness in the wheel can also come from tie rod ends. It's best if you have someone help you. Have them move the wheel around while you look at the ball joints and the tie rod ends. If it all looks tight, then the bearings are pretty worn. You might be able to get by with tightening them, but I'd replace if they're so worn they're sloppy.

 

If you go 12 and 6 o'clock, you'll be checking the ball joints/wheel bearings. If you have your hands on 9 and 3, you'll be checking tie rods

The 12/6 goes up and down where as 9/3 go side to side as if you were turning the tire by hand. The tie rods won't come into play if you go 12/6.