The purpose of the shock absorber is simply to limit the motion of the spring during compression and rebound cycles. If the vehicle is not equipped with these motion dampers, the up and down motion would multiply until the vehicle was alternately trying to leap off the ground and to pound itself into the pavement.
Countrary to popular rumor, the shocks do not affect the ride height of the vehicle. This is controlled by other suspension components such as springs and tires. Worn shock absorbers can affect handling; if the front of the vehicle is rising or falling excessively, the "footprint" of the tires changes on the pavement and steering is affected.
The simplest test of the shock absorber is simply push down on one corner of the unladen vehicle and release it. Observe the motion of the body as it is released. In most cases, it will come up beyond it original rest position, dip back below it and settle quickly to rest. This shows that the damper is controlling the spring action. Any tendency to excessive pitch (up-and-down) motion or failure to return to rest within 2-3 cycles is a sign of poor function within the shock absorber. Oil-filled shocks may have a light film of oil around the seal, resulting from normal breathing and air exchange. This should NOT be taken as a sign of failure, but any sign of thick or running oil definitely indicates failure. Gas filled shocks may also show some film at the shaft; if the gas has leaked out, the shock will have almost no resistance to motion.
While each shock absorber can be replaced individually, it is recommended that they be changed as a pair (both front or both rear) to maintain equal response on both sides of the vehicle. Chances are quite good that if one has failed, its mate is weak also.
REMOVAL & INSTALLATION
See Figure 2, 3 and 4
The usual procedure is to replace shock absorbers in axle pairs, to provide equal damping. Heavy duty replacements are available for firmer control. Air adjustable shock absorbers can be used to maintain a level rid with heavy loads or when towing.
- Raise and support the van.
- Support the rear axle with a floor jack.
- If the van is equipped with air lift shocks, bleed the air from the lines and disconnect the line from the shock absorber.
- Disconnect the shock absorber at the top by removing the nuts, washer and bolt.
- Remove the nut, washer, and bolt from the bottom mount.
- Remove the shock from the van.