The ability of the Toyota shock absorber to limit the movement of the body in a vertical motion is what reduces the wear on the many other chassis and suspension components on your vehicle. This is a closed loop hydraulic system on your Toyota that will last for many years under normal conditions. Just like all other hydraulic systems with metal components, the joints where the metal is joined together are sealed with a polymer material. It is these seals that will rupture in time causing the hydraulic fluid to leak out inhibiting the shock absorber from performing its task of reducing excessive vertical movement of the body. The body of the shock will then also have hydraulic fluid on it. If the load experienced by the shock absorbers is too great, the seals in their system will rupture. They will also just rupture over time of being used. To know if this has occurred on your Toyota, a bounce test of the vehicle can easily be accomplished. This is done by depressing one corner of the vehicle and releasing it. The body of the vehicle will then rise and fall. The more times this vertical movement is observed, the greater the wear on the shock absorbers exists. The replacement of the Toyota shock absorber is warranted if the body of the vehicle moves more than one time in the bounce test. On all Toyota models there are either two or four shock absorbers depending on your drive type (front-wheel vs. rear-wheel vs. four-wheel) and type of suspension. Instead of having a shock the front wheel drive models have Macpherson struts. This is a suspension component that replaces both the shocks and the springs. That suspension component is tested the same as the shocks are.