Help! front suspension/ steering issues!

[Hitchhikingmike]

I've been having some trouble with my 2002 4.0 explorer with 50k miles on it.

If you could help me diagnose I would greatly appreciate it!

One day I hopped in the truck to drive around the city. The first turn I made out of the driveway the steering wheel shook violently. Every turn I was making at low speed, the steering wheel would violently shake up and down. It shakes not only while I am turning the wheel, but after the wheel has been turned while the truck is still turning. No it is not the power steering and I do not have any air in my power steering lines. I know what it feels like to have air in your power steering lines and this is much worse!

Other wise the truck runs as smooth as butter in straight lines.

Next I jump onto the highway and as soon as I reach 45mph the steering wheel began to violently shake up and down again. As soon as I slow under 45mph the truck rides smoothly. When I pass 45mph the steering wheel violently shakes up and down. The truck can still hold it self in a straight line and the wheels do not appear to be out of alignment to the eye. Just whenever I turn left or right in the city and with speeds over 45mph the steering wheel violently shakes up and down.

Here is the weird part: after driving around the city like this for about 20 minutes all the problems went away. I could smoothly turn the truck left and right and the truck would smoothly sail at 75mph on the highway.

I jacked up my front end and checked the wheels for play, and could not get any. I tried to shake the wheels in every direction and they were solid. The wheel bearings appear to be in great condition and I cannot get any play out of the ball joints by man handling the wheel on the truck. I check over the knuckle, upper and lower control arms and the complete steering rack and could not find any bent/cracked/lose pieces. The front wheels do not appear to be out of alignment to the naked eye. I stared the wheels down for a good 10 minutes trying to notice anything weird about their camber/caster/ tow in/out and the wheels appear to be perfectly aligned. The truck also drives perfectly in a straight line on its own, no pull to one side or the other.

I recently got new tire up front about 2 months ago. So the front wheels have been balanced within the past 2 months. All the weights are still on the wheels too. So I know that my wheels are balanced.

Ever since the one incident the explorer drives great now. I am at a complete loss of words for what happened. I am just a bit worried of this repeating itself while I'm on the highway going 75mph.

Although the truck drives/handles great now, I feel that when I go over bumps I can feel the jarring of the bump more so in the steering wheel then I could before. Although the steering wheel has no play to it in the steering at all.

Can a shade tree mechanic diagnose what's wrong by himself and try and avoid taking it to the stealership? Anyone knowledgeable want to take a stab at my issues here?

Thanks.

[Hitchhikingmike]

Okay, I lied, I did have air in my power steering system. Sorry for the long winded previous post. I remember now that before this happened I was moving the wheels around on jack stands with the engine off. I did not know this allows air into the power steering system.

Now the only issue I have now is that for every bump in the road, I can feel it in the steering wheel that I did not feel before. The steering wheel has a kick back effect to it. I didn't use to do this. Do you think this is a symptom of bad ball joints?

Thanks.