According to Herth+Buss, worn or defective shock absorbers should always be replaced for all wheels on the axle in question. Replacement of one single shock absorber will exacerbate the difference in performance. Here, the company provides an overview of the correct procedure.
Loosen the nuts from the top strut mounting on the suspension strut dome to enable these to be unscrewed by hand at a later point in time.
Tip: treat rusty connections in advance with an appropriate contact spray.
Raise the vehicle and remove the wheel.
Now loosen all bolts on the shock absorber and remove the full sensor system and the brake line. Depending on the age of the vehicle, it may also be advisable to use a contact spray in this case.
Once you have removed all the nuts and bolts from the top strut mounting, the exposed suspension strut can be removed in its entirety.
Tip: depending on the design of the vehicle, the stub axle may need to be propped up in order to prevent it from falling.
On the removed suspension strut, mark the position of the individual strut components with a continuous line to ensure smooth re- installation.
The next step is to compress the suspension strut using a spring compressor. Once the spring is sufficiently compressed by the spring compressor, the nut can be loosened from the top strut mounting, and the top strut mounting can be removed together with the spring cap. Remove the exposed shock absorber from the spring.
Ideally, you should replace all rubber components and install these on the new shock absorber. When mounting the spring cap on the suspension strut, it is important to ensure that the guide mount sits on top of the one on the shock absorber. Now screw the top strut mounting and the spring cap to the shock absorber.
Tip: on older vehicles, it is also recommended to replace the top strut mounting at the same time, as this will avoid any additional work at a later point.
Relax the spring and ensure it sits correctly in the spring caps.
The assembled suspension strut with the replaced shock absorber can now be installed on the stub axle again. The same applies for the previously removed sensor system and brake line.
Finally, tighten the nuts on the top strut mounting and shock absorber fully once more. It is imperative that you perform an axle alignment after replacing a shock absorber, a coil spring or a top strut mounting.