I bought replacement shocks for the front, at 117K the ride was getting way too bouncy. My indy quoted $245 labor so I took it to him. He had the car for a half day and called to say that all his spring compressors were not up for the job, he refered me to an import alignment/shock guy down the road. His compressor gave way and sent his guy to the emergency room for stiches. I still don't know how badly he was hurt but just a word of caution on this job. I'm sure 4Matic shocks are replaced without incident every day, just be very careful, those compressed springs have a the potential to inflict very serious injury.