At about 50,000 miles on my 2000 4Runner I could feel the rear axle bouncing a lot more due to the rear shocks getting weak and replaced them..

I believe that the heavy weight of the rear axle and not to mention heavy larger tires does a number of the shocks pretty quickly..

Noticeable improvement when I replaced the shocks.. Still running the original front shocks however..

2000 4Runner,V6,Auto,31's, Sliders, Skids, On-Board Air, Air Shocks
Related Interests: Welding, Ham Radio, Road Tripping (Blue Highways), High End Video/Audio Systems