My 2002 Trailblazer started rocking side-to-side earlier this year while driving down the highway. As speed increased the condition worsens to a point I need to slow down to stop it. I have a sense the rocking starts in the rear of the SUV but I’m not sure. I have checked the Sway Bars & Bushings, which are original, and they appear in good condition and tight. I have Bilstein shocks with 140,000 miles on them, with no leakage and they appear to be working correctly. I have not checked the small stabilizing links. My 2-ply Yokohama tires were put on 30,000 miles ago and I did not have this problem when they were originally installed. Any idea what is causing this?