Tech Article Title Author Date
Improved Driveline Control Don Pavlik 2001

As an owner of an S4 I've been known to depart from a stop at a "slightly" greater than normal pace more than once or twice. 2.7t torque, quattro, some throttle and a quick foot on the clutch will pin a passenger to the seat and leave most traffic in a big hurry.  But I wondered... just what is going on under the car when I decide to drop the hammer? I had addressed my concerns last year with the addition of the (now discontinued) UUC Motorwerks Audi Driveline Stabilizer (ADS, henceforth) but I recently rode in a car with APR's snub mount and was impressed how firm the shifts were compared to my car.  Could this rather inexpensive, small mount really deliver the goods compared to the beefy hardware of the ADS?  I had to know.

In my quest for knowledge I purchased a snub mount intent on putting the snub and ADS head-to-head along with a stock configuration to see if they really were any better. I installed the ADS on the car last year so I tested it first then removed it, ran the car stock then installed the APR snub mount and left the car in that configuration to get a feel for how the mount performs in day to day driving compared to the ADS. To compare the three configurations, I mounted a small camera under the car with a view of the transmission then put each configuration through the same regiment. Not intent on abusing my clutch or the rest of the car too much I decided on the following: 

  • Standing start, revs steady at 2,400 rpm
  • Quick release of the clutch (no side-stepping here folks), full throttle 
  • At 6,000 rpm do a quick shift into second
  • Pull 2nd to 5,000 rpm then chop the throttle while still in gear

The hardware

Stock snub and APR snub mount

UUC Audi Driveline Stabilizer


Watchful eye:  .5 lux color bullet camera

The results

Runs completed, I stepped through the video of each run frame by frame and did still captures of the drivetrain position at rest and the extremes of launch, shift clutch-in, shift clutch-out and throttle chop while in gear. My apologies for the poor image quality; evenly lighting the transmission area proved to be rather difficult. 

In the sequence of frames below the lines drawn across the pictures indicate the idle position and the launch extreme. The lines extend across just to provide a reference for the remaining frames. On the stock sequence I also marked the extreme of movement when I chopped the throttle. The chopped throttle movement of the snub and ADS drivetrain was so small from idle that marking the chop position just added clutter to the images. 

The point of reference for the horizontal lines is the horizontal edge of one of the transmission housing reinforcements. The reference point is about 6" from the end of the transmission so total tailshaft movement is more than the indicated scale not to mention that that angle of the camera view probably distorts things a bit. My trig skills fail me so you'll have to figure out the total movement of the tailshaft at the end on your own. 

Markings explained


Stock  APR snub  UUC ADS

The stock configuration allowed for a significant amount of movement compared to the snub and ADS--almost one third more at launch. At shift clutch-in for the shift to second gear the driveline sprang back almost to the at rest position and then at shift clutch-out moved back nearly to the launch position. When the throttle was chopped at 5,000 rpm the drivetrain did some more traveling continuing past home and then some. All this movement can easily be felt as slack in the drivetrain bumping around. Yikes.

ADS vs. snub... here's the skinny. At launch, the APR snub mount performed ever so slightly better than the ADS--the movement extreme was just a teeny bit more with the ADS. At shift clutch-in with the ADS the driveline moved back to the at rest position while the APR snub driveline didn't quite return to at rest. I'm guessing since the ADS has a more compliant rubber mount compared to the snub's harder material it was more likely to spring back once the load was removed (also probably why ADS launch movement was slightly more). On the return to neutral point I'm not sure which is better.  Is it better to have everything move back to "neutral" while you're fiddling with the gear shift lever or is it better to have less movement overall? I can't decide. 

At shift clutch-out the snub driveline moved back to the same position as launch while the ADS halted movement at less than 1/2 of the launch movement which is A LOT less movement than stock! Compare the 1st and 4th frames to see what I mean. On shifts and throttle roll-ons the ADS certainly offers an improvement.

Surprisingly, when the throttle was chopped in gear at 5,000 rpm both the snub and ADS driveline returned to the at rest position. Both offered excellent control.

What the movement extremes don't show is the wiggling and jiggling going on during all my futzing about.  Here, the ADS edged out the snub and made the stock mounts look like they were simply out on vacation. ADS movements were slower and more controlled. The ADS also offered better side to side control of drivetrain movement.  Take a look at the video of the runs--you'll be surprised.  

Driveline movement comparison (1.59MB) RealVideo

I do have one concern with the ADS however... namely, it appears it would obstruct the transmission from pivoting down in the rear in  the event of a front end collision that pushed the engine back. It's attached to the car with the engine cradle subframe bolts and is heavy steel construction--this puppy aint goin' anywhere in a collision.  Unfounded concern?  Who knows. It doesn't bother me much--it's been on my car for over a year. 

In daily driving, the APR snub mount shifts feel firmer than those of the ADS. If you want firm shifts look no further than the APR snub mount! Great for testing the neck muscles of naive or unsuspecting passengers. : )  Noise-wise the ADS adds a bit of engine noise around 4,000 rpm (mostly felt in the footwell) while the snub transmits some vibration to the body if you lug the engine at very low RPM.  I only notice the vibration when I'm creeping along in rush hour freeway traffic and ease out the clutch in a gear too tall or if I do a slow start in from a stop in 2nd gear (which I do often in traffic).  Otherwise,  the APR's snub mount didn't add any additional noise. 

I do prefer the driveline control of the ADS in slow traffic situations. It damps the "bump" and "rubber banding" of the driveline when using light to no throttle in a low gear, again, while creeping in traffic.  I can also imagine it as a very worthwhile addition for someone who drag races or who subjects the drivetrain to extreme duty--having an extra mount point will relieve stress elsewhere.

Price wise you can't beat the APR snub mount--an excellent value (around $50) and a definite improvement over stock.  I paid $329 for the ADS which, of course, is no longer available so I guess the price is really a moot point.  

Is the ADS worth the extra $$$?  If you're hard on the car (hard launches, hard shifting and such) I'd consider it a worthwhile investment. If you drive easy and "rubber banding" is not a pet peeve of yours, probably not.  Would I buy the ADS again? You betcha. Does APR's small inexpensive snub mount stand up against the big-n-beefy ADS?  In most cases, yes.

Hmmm.... APR snub + ADS, that sounds like an interesting combination.

Please note: The UUC Motorwerks ADS reviewed here is not the same stabilizer as offered by AWE Tuning. AWE's DTS is similar in concept to the ADS but at this time I have not reviewed their product nor do I have any information or specifications regarding the AWE DTS. 

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