I heard lots of positive comments about the UUC Audi Driveline Stabilizer (ADS henceforth) so I decided to get my S4 one for her birthday (Oct. 12). Since I didn't want to make her wait to open her present (birthday falls mid-week this year) I gave it to her early so we could install it right away.
The ADS is a stout piece of hardware with heavy plate steel ends with a beefy center section. Looks well made and it's finished well enough for a piece that will forever live under the car. As usual with everything I buy I was short one piece of hardware (one washer). Took me about an hour to install since I was doing it on ramps, taking pictures and making mental notes. Actually, I spent more time getting the car up on my ramps than I did on the actual install. My ramps provide 9.5" of lift but the approach angle of the ramps is so steep that the nose of the car hit the ramp before the tire was within 4" of the ramp. Damiiiiit. I had to add on to the ramps with some 2x8s to get her up in the air. In case you're wondering, the wood add-on is secured with 3/8" bolts to the ramp itself so nothing moves.
The difference in the feel of the car is pretty amazing. Gone is the slop in the driveline I normally experienced while creeping along in traffic while in 1st or 2nd gear. Before installing the ADS if I lifted off the throttle in 1st at about 2,000 rpm the car would yo-yo (Car and Driver called it "rubber banding") while the mass of the car and the torque of 1st gear fought each other. Btw, this yo-yo feeling is not unique to the S4... most other cars do the same thing. IMO, the reduction of just this annoying behavior makes this mod worth the price all by itself. Other benefits are crisper, more positive feeling shifts and a more positive feeling when letting out the clutch quickly.
The only downside I see at this point is an increase in driveline noise transmitted to the interior and a vibration that can be felt in the floor if I hold the engine around 4,000 rpm. I checked the alignment of everything and verified that the exhaust was not hitting on the center brace (it's very close on the passenger side) but all looks good. I guess if everything is held more secure a little more noise is to be expected -- not a big deal, just an observation. My only other issue is that the brace would probably prevent the transmission from tilting down and away in the event of a front end collision -- may not be an issue, dunno.
UUC documentation is good but pictures would have been nice.
I suspect other performance vendors will soon offer an ADS type of brace of their own if they have any common sense... nice modification.
After some driving around for things to settle in and more aggressive driving I found that the RH section of the exhaust was hitting on the bar. This was very obvious as a noise resonated through the car. The instructions mention if you have a clearance problem to install additional spacers between the transmission and the new mount. I put in an extra pair but it it was not enough to solve the problem. Putting an 2nd pair would have put the transmission and the bar under constant tension once everything was tightened down. I contacted UUC but their comment was just additional spacers. Hmmmm, not possible. After some more fiddling I decided to "make" room by putting a chamfer on the back edge of the bar where clearance was tight. See updated installation instructions below that should eliminate the need to do any modifications to the bar.
Revised Installation Instructions
How to properly install the ADS. (courtesy of