What would cause the 2004 Chevy TrailBlazer rattling noise?

A bad sway bar end link is in a 2004 Chevy TrailBlazer a very common reason for a rear-end suspension rattle, probably the #1 cause in most cases. Sway bar end links are the attachment points between a sway bar and suspension members. Also known as a stabilizer bar or anti-roll bar, the sway bar connects suspension components on either side of the car to MINImize body leaning in turns. Though the sway bars themselves are made of long-lasting, durable steel, the end links incorporate bushings that can fail with age and wear. That can introduce play that causes noise, compromises the sway bars effectiveness, and may lead to separation. Inboard sway bar bushings, which serve as a hinge, also must be maintained properly.