Blazers aren't built they're slammed together... One day I noticed a severe knocking noise coming from the rear passengers side. It was loud enough to sound like someone was slamming a boulder against my rear quarter panel, once I investigated the source I found that the bushings connecting the two halves of the tire carrier were wearing into the mounts on the body. So when I would go over bumps the mass of the tire moving up and down would slam the bushings into the mounts making that horrible noise. The body mounts are made of cast steel which is brittle and soft, the bushings are likely made from a harder mild steel.

So as the carrier is moved with the tire the bushings wear into the softer metal which the mounts are made from. Massive problem... so easy to avoid. Just use forged steel not cast!!