C7 S6 Front air strut clunk?

Dealer says front air struts need replacement. They don't leak and car handles great but getting suspension drop thunk into certain types of road bumps. Was thinking the strut mounts may need replacement rather than the whole unit. Does anyone know if they are a replaceable part on the air strut assembly or is this really a single unit that isn't serviceable in a home garage?

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I should add that the upper and lower control arm bushings and sway bar end links are already replaced.

Air struts don't have rubber strut mounts that are removable AFAIK, unlike the A6 or other coil/spring setups. I had something similar and ended up replacing all control arms to get rid of the noise. I most likely had a bad ball joint that would clunk over bumps at low speeds. But before go spending thousands, there are a few more things you can check.

1. Tightness of the strut mount tower brace triple square bolts (https://www.youtube.com/watch?v=p2kil_I64to)
2. Tightness of the nuts that hold the air strut to the strut tower (30 Nm - x4 per side)
3. Lift the car and shake the wheel back and forth with hands at the 12 and 6 oclock positions to check for play. Similarly check for play using the 9 and 3 oclock positions.
4. Take a pry bar and wedge it between the lower rear and lower front control arm to check the ball joints for play (helps if you setup a camera in a fixed position and record - can be hard to see slight movement of the ball joint if your head is also moving)
5. Tightness of the front subframe bolts (115 Nm - x2 per side)
6. Tightness of the chassis brace bolts (90 nm - x8 total)

The noise you are hearing is coming from the strut brace. It has a tendency to get loose. Tighten it down with some locktite and you'll be fine.

I am glad I read karlito's comment, mine has recently begun doing the same thing and I haven't looked at it, if the brace is loose I will lol.