My 64 F100 2wd will run straight until I hit a bump, then suddenly it runs in a different direction. The guy who sold me the truck said the manual steering box was rebuilt, after trying to adjust it{does not help} I suspect it might be the king pins? Any input would be a great help.

 

Brian,
Look for wear in all components; tie rod, drag link, king pins. shocks, shackles, weak springs, etc. Many times additional caster helps these straight axles. Good luck
ray

 

Hi Brian-I'd try a Steering Damper first, usually 40 bucks or so. If it's King Pins (which if you don't know the trucks history is a good thing to rebuild anyway) the front wobbles alittle bit all the time, and causes inside edge of tires to be cupped. Good Luck

 

Don't overlook the wheel bearings! I found a loose one on my '70 F100 and tightening it made a noticeable difference.

 

IMO, a steering damper is a bandaid. If you have worn parts a damper is not going to help much. BTW, check your tire pressure.
ray

 

The king pins are a likely suspect, as each of my '64s has needed to have them replaced. However, the type/condition of the tires also makes a noticeable difference. For example, I have a clapped-out '63 with decent radial tires that handles far better than my much nicer '64 with original-style bias ply tires.