Jill's correct on both points, mejds. While not traditional-bed pickups in the usual sense of the term, both the Avalanche and Escalade EXT were derivatives of the Chevy Suburban/ GMC Yukon platform. That platform used a traditional solid beam rear axle, not IRS. It used the solid beam because of its durability for towing and carrying heavy loads. And the picture you posted was indeed simply coil-springs...not necessarily IRS. An IRS, no matter what specific type of suspension, allows each rear wheel to bounce up and down independently without impacting the movements of the other one, and without transferring any of the impact forces through a heavy, solid rear drive-shaft or beam-axle.

However, that does not mean that a beam axle is necessarily an inferior design. It can be quite effective if done properly. My Buick Verano, for instance, a small-to-medium size car by today's standards, has a beam axle, yet IMO rides and handles better than some other cars its size with IRS.