The brief
The SLK350 had picked up front-end vibration and creaking noises going over road humps, the signs that something up front in the suspension wants attention. He brought it in. The culprit was the anti-roll bar links. The anti-roll bar runs across the front and ties the two sides of the suspension together so the car leans less in corners, and the links are the short rods with ball joints and bushings that connect that bar to the suspension. The bushings crack and the joints wear, so over a bump the link works loose and rattles or creaks, and the anti-roll bar can't do its job cleanly. Left unchecked, worn links put extra stress on other suspension components and lead to uneven tyre wear, so they need changing.
The diagnosis
On the lift the front suspension got a full safety inspection of the wear-and-tear components. The anti-roll bar links were the cause, cracks and failure in the bushings with play in the joints, which is exactly what makes the creaking and the front-end vibration over humps. The rest of the front suspension checked out. When the links on an axle have gone, you do the pair, they wear at much the same rate, and a fresh one next to a worn one just means you're back under there soon for the other side.
The work
Both front anti-roll bar links were unbolted and removed, and a new pair of genuine Mercedes-spec links fitted, the ball joints torqued to the manual figures and seated properly, the fresh bushings checked. The rest of the front suspension was given a final check while everything was accessible. A road test confirmed the creaking and the vibration were gone, the front end quiet and tight over humps and through corners. The job was finished off with a complimentary wash and an interior vacuum.
The outcome
No more creaking or vibration from the front, the anti-roll bar working properly again, the car flat through corners, and a tidy front end. The SLK350 went home with the noise sorted. Worn anti-roll bar links only creak louder and put strain on the parts around them, so doing the pair put the front end back to quiet, the small job that protects the bigger ones.