Get under the front end of your truck and spend ample time (10-15 minutes) inspecting every single component of your steering system. What you should be looking for is anything shiny on rubber, steel, or polyurethane components, since that is a sure sign that something’s moving around that shouldn’t be. As stated earlier, the track bar should be your main focus here. Loose bolts are a killer, so check everything you see for tightness.
If that all checks out, go get your truck aligned at a good shop. Note: if you’ve got a lift kit on your truck, make damn sure the shop is smart enough to use the right specs on your alignment, because it’ll be different than the default specs.
Other things to check include your ball joints, the track bar mounting bracket bolts, steering box bolts, and track bar ends. Basically, you want to make sure that track bar is behaving exactly as it should, so also look at the bushings to make sure there’s no play there and that they’re not worn out.
At this point, if you’re still having issues, there’s a possibility your hub bearings are going out. They obviously can wear out like any other mechanical part, and any slop in them can contribute to the oscillation, but they’re rarely going to be the actual source of your issues. Just something to check. By now, you should have pinpointed the problem somewhere along the way and can take steps to resolve it. It may not be cheap, but it’s better to do it right the first time and actually get it fixed properly.