I,ve got a 74 f100, driving along at highway speed, all of a sudden it will start to vibrate badly. It will shake the steering-wheel out of your hand. You can slow way down and it will stop, then you can regain highway-speed and it may not do it again for a couple of days. It almost seems like it will hit a little bump before it starts the vibration. My brother has a late 80s ford truck and it has started doing the same thing as mine. We,ve rotated tires and checked suspenion, checked brakes. Is this a common problem with these trucks? We haven,t found the problem yet. thanks

 

Oily,
There is a possibility of mutiple problems here. My guess is you need shocks. An under damped vehicle can go nuts on you once a problem is set loose. "Loose" is the key word here. You've got to inspect the front end suspension:
1.Front end king pin bushings.
2.I-Beam bushings.Pilot arm bushings.
3. Steering gear box.
4. Tie rod ends
5. Pitman arm
6. Shock absorbers
7. Front wheel bearings.
I will assume that the tires are fine.
The first two are most likely to hide until you hit a bump.
You must have play in something for the front end to shake. Find what's loose and your set.
My Way is the Highway,
KingFisher

 

4x4 or 4x2????????

 

I want to thank everybody for the posts. The trucks are 2W-drive. Thanks