REAR SHOCKS - WHEN TO REPLACE
In vehicles with a solid rear axle, the rear shocks typically mount from the frame to the spring plate that attaches the leaf springs to the axle. Shocks are used to dissipate energy and can be filled with hydraulic fluid or air.
Several warning signs can tell you when shock absorbers need replacing. If your car bottoms out when driving over railroad tracks or other dips in the road, that's a key warning sign. Other warning signs include unusual noises when driving over bumps, or excessive body lean in turns.
One way to test shocks is to push down hard on each corner of a vehicle. If the car continues to bounce after you let go, your shocks need replacing. But, this test needs quite a bit of strength. With many high-riding SUVs and pickups it isn't easy to get the necessary leverage.
Instead, you should have a qualified mechanic put your car on a lift to check your shock absorbers. Shock absorbers are filled with fluid. When there are worn mounts or bushings, or physical damage such as dents, they leak. A mechanic will be able to see if there are major leaks.
Some recommend replacing shocks at specific intervals, such as every 50,000 miles. But, when you actually need to do it can vary by vehicle and by how and where you drive. Driving over rough, pockmarked roads puts more stress on the shock absorbers. You will need to replace them more often if you drive on rough roads more than on smooth pavement. Carrying heavy loads also will wear out shocks faster.