Let me start by saying that I'm taking my car to the nearest Audi dealership to have this problem looked at, but I can't get it there (150+ miles away) until late next week. I'm hoping to learn something from all of you that will help me be sure that the Audi techs diagnose the problem correctly or (even better) will give me enough information that someone local can pinpoint the issue.

Car and Mod Info (in case any of the mods are relevant)

• 2005 (B6) S4 with 6-speed manual (47,8XX miles on the odo)
• VMR 710 19" wheels
• Bilstein PSS9 adjustable coilover suspension (The seller told me they were set near the lowest ride height and at about 90% of max firmness)
• Milltek down-pipes and exhaust (resonated)
• APR Stage I chip

Symptoms

• Mild vibration that I can feel both in the steering wheel and through the body.
• Sound that is probably best described as a knock or thump with a characteristic that I'd call "flutter".
• I get the sense that the sound is coming from somewhere near the right-front wheel, but I can't quite pin it down.
• The sound and the vibration vary proportionally with speed -- the frequency of the vibration and the volume, pitch, and interval of the sound all increase at higher speeds.
• The sound is audible at speeds as low as 15 mph.

Conditions

• The sound occurs only if the transmission isn't engaged (clutch depressed, or in neutral) or at zero/zero throttle point -- it goes away under acceleration or if I left off the throttle completely while the car is in gear. It also goes away if I'm braking more than what I'd consider "lightly".
• The sound occurs almost exclusively when there is load on the steering wheel to the right, but it doesn't have to be much load at all -- simply moving the car from the left edge of a lane to the right edge will trigger it. I say "almost exclusively" because I've heard a little bit of it on rough roads or going over the large speed humps that you find in some residential areas. Turning the wheel slightly back to the left will stop the noise, but it returns as soon as I tip in to the right again.
• It seems to be more prominent in higher temperatures and when the car is warmed up. First thing in the morning when it's still cool (that's a relative term -- here in south Texas in August it's usually in the range of 82-87 degrees at 7:15 A.M.) I don't get any symptoms, but at lunch or late in the afternoon when the temperature is up in to the mid-to-high 90s it seems to happen much more frequently.

Things I've Considered and/or Eliminated

• Tire Pressure -- all four tires have been inflated to 32 psi and when checked had been in the range of 29 to 33 psi.
• Driveshaft Carrier Bearing -- On a suggestion from another mechanic, I considered this possibility but haven't wanted to pay for someone to pull the driveshaft to look into it. (see this for reference: http://www.elektro.com/~audi/transmission/#driveshaft, which actually led me to the next item)
• CV Joints - a local mechanic (who I've been told is the best bet for German cars in the area) did my recent oil change and while he was at it, he tried to find the problem. He couldn't see any issues with the CV joints, but strongly suggested that I get the car to the Audi dealer as soon as possible to get it documented before the car hits 50,000 miles and the factory warranty coverage ends.

Ok, ye gurus of Audi wisdom... any ideas?

Thanks in advance.

P.S. First-time poster... be gentle with me.

 

checked your control arms yet?

 

No, I haven't had them looked at, but I'll see if I can get someone to check them out this week. Thanks for the suggestion.