At highway speeds above 60 mph on a smooth road, the vehicle runs fine. But if the road has any bumps at all, even small ones, it starts to vibrate very fast as long as there are bumps. The steering wheel almost becomes a blur. It’s like it’s going into oscillation.
The wheels have been balanced and rotated. The movement the steering wheel is not side to side, like I have experienced with imbalanced wheels.
The shocks look fine and I am told that they are OK by the tire dealer . I have never had this kind of a problem with bad shocks. The vibration is just too rapid.
Before I take the truck in for the mechanic to inspect it, I would like to hear some ideas as to what the problem might be.
Phil, sounds to me like the classic symptoms of a bad steering stabilizer, sometimes referred to as a steering dampener. It Looks similar to a shock absorber and should be attached to the center, or drag link. You can look at it to see if it’s leaking, or even unbolt it & check to see if the rod moves way too easily.
There are plenty of things that it might be so I think you’re just going to have to wait to hear what a shop has to say. I’d be wanting your best, local front-end/alignment shop. The options include defective tire (I’ve had them proclaimed “balanced” & still be a problem), bent/damaged rim, tie rods, ball joints, wheel bearings … Some of those are dangerous - don’t wait.
Count my vote with cigroller about checking suspension and steering components and their being dangerous. The vehicle is 20 years old and if things like ball joints, tie rods, tie rod ends, wheel bearings, etc. have never been replaced then I would be stunned if one or more (or all of them) were not worn out.