The brief
The Passat had a loose feel through the steering wheel on-centre, a clunk every time the wheel went lock to lock at slow speed, and the lever test under the car showed visible play at the ball joint. Three signs of a worn lower arm.
The lower control arm locates the bottom of the front wheel and lets it move up and down over bumps, riding on rubber bushes, with a ball joint at the outer end that the steering knuckle pivots on. When the bushes crack and the ball joint develops play, the wheel can wander a little on its own, which is the loose feel, and the slack knocks when the steering loads up, which is the clunk. The geometry drifts with it, so the tyres wear unevenly.
The diagnosis
The visual confirmed it: cracked bushings in the lower arm, and the ball joint with movement past spec. That's a worn arm, and the right fix is the arm as a complete unit with a fresh ball joint fitted, not trying to nurse the old one.
A four-wheel alignment went on the list for after, because new suspension parts reset the geometry and the car has to be measured back to factory camber and toe.
The work
The car was lifted, the ball joint disconnected from the knuckle, and the failed lower arm dropped out with its ball joint. A new VAG-spec arm went on with a new ball joint, the chassis bolts torqued to spec.
Then the car went onto the alignment rig and the front camber and toe were set back to factory.
A road test confirmed the steering was tight and the car tracked straight on a flat road.
The outcome
The steering is tight on-centre again, no clunk on lock to lock, and the car tracks straight on a flat road.
The Passat went home with the front suspension proper. Replacing the arm with a fresh ball joint and aligning it afterwards means the wheel is located the way it should be, the clunk is gone, and the front tyres will wear evenly again instead of scrubbing an edge.
