Disclaimer:
Do this at your own risk. I decline all responsibility for any damage you may do to yourself or your vehicle.
This is actually quite a straightforward job. Other than the slight complication of the DRC, the job is essentially the same as on any other A6.
Prerequisites:
- Spring compressor
- Open ended pipe wrench (18mm I *think* IIRC) for assembling the struts.
- Set your PSS9s to 4. Useful setting range is 1 to 4. Anything above 4 and it's underdamped and your ride will be rubbish. (I started at 6 and I can tell you that the ride at 4 is more comfortable than at 6).
- Replace the top mounts for the front and rear. Part numbers are:
2 off 4D0 412 377 F
2 off 8E0 512 121 D
&
I started at the rear.
For the rear:
- Remove the road wheel. Don't take any risks, use axle stands or other safety devices. People die when cars fall on them - more frequently than you might think. I always use axle stands, even if I don't intend to get under the car.
WARNING: DRC operating pressure is 16bar. This is more than enough to inject the fluid into your bloodstream and kill you, so I advise wearing heavy gloves and saftey glasses. The reality is that probably only a tiny dribble will come out, but why take the risk?
- You'll see where the flexible pipe goes into the DRC shock. Follow it back a bit and loosen joint. Let any pressure relieve slowly. Use a bowl to catch any fluid that escapes.
- You can close off the pipes if you like. One of mine was seized to I had to saw it off - no going back! Usually if you're installing Bilsteins you have no intention of going back to DRC anyway...
- You can remove the central valves if you want. Looked like a lot of work for not much gain to me so I left them in place.
- Now to remove the strut. First remove the caliper and disk and put them to one side (obviously, don't disconnect the caliper, just suspend it to one side). Also remove the heat-shield or you'll probably damage it.
- Loosen the ARB
- Remove the figure of 8 link that connects the ARB to the subframe. I couldn't remove the strut without completely removing this "8"
- Remove the following bolts:
- Remove the 2 bolts that hold the upper mount to the body of the car and you should be able to remove the strut. You'll have to press down hard on the subframe. I managed to press it down with one foot and pull the strut out. I must have looked like a right contortionist.
- Put together the new Billy with the new upper mount and fit it. You'll need the spring compressors.
- Tighten everything back up using the new bolts you got in the kit.
For the front:
I found this to be much easier than the rear.
- Disconnect the DRC in the same fashion as for the rear.
- Open the bonnet and locate the 4 rubber grommets that hide the nuts for both struts' upper mounts. You'll destroy them when removing them. I bought some new ones but I can't see what possible use they might have and you can happily leave them off.
- Remove the 4 nuts (circled in green) from the upper mounts. DON'T touch the other bolts (red crosses) or you'll have to have the complete geometry set properly again (not just the tracking, the whole hog). Also be careful of the A/C plumbing. They run right in front of one of the nuts and you'll have to tease a tool past them.
- Break apart the ball joints of the upper arm. Personally, I never use ball joint spreaders (haven't got one
). I just hit the housing with a hammer and the ball joint pops out. Use whatever technique you're comfortable with. Don't mess with the steering control rod. 
- Here's one I did earlier:
-Remove the bolt from the bottom of the strut (in green). Press down on the lower arm to release the strut and pull it out. BE CAREFUL not to damage the level sender (circled in red).
- Put together the front PSS9 using the metal part of the mount you'll have removed from the old strut. Slide your new rubber mount into it. Then put it in the car the same way you removed the old one.
- Reassemble everything using the new bolts supplied with the kit and torque it up (with the car on the ground for the purists).
All you have to do now is adjust the height. I started with the fronts then adjusted the rears to match. I wanted stock height, so I put mine up as far as they'll go at the front. Things'll settle, so you may want to check and re-adjust after a month.
To adjust the height, use the tools provided in the kit. Jack up the side of the car you want to raise (so you're not working against the spring) and put a mark on the adjustment nut. This way you can count how many times you've turned it and do the same to the other side of the car. Unless you want a lop-sided look. Each to their own...
Then take the car out for a drive and seriously congratulate yourself for buying the billies.
And yes, I know that my CV boot is split
It's fixed now.
