Over time, my '01 Chevy 2WD with a 5.3 Liter began to make a knocking noise and vibrations that could be felt through the steering wheel. It was so bad that I wondered if the vehicle's suspension was going to fall apart on me, and, due to age and mileage, if it were worth fixing. Many an upper steering shaft have been replaced for hundreds of dollars over this issue, only to have the problem return. Here's how to fix the problem for $3.
Look under the driver's side dash; if like mine, it looks pretty clean except for the yoke connecting the steering wheel to the upper intermediate shaft. That yoke was so dusty that it looked like a chia pet. Also, where that shaft goes through the firewall was some corrosion. I cleaned both areas and gave both spots a spray of WD40, and the problem disappeared. That was over 4 years ago and that noise and vibration have NOT returned.