This is tuff to do without feel. Have you verified the harmonic? Is the vibration engine, drive shaft or axel speed, drive shaft seems like the most likely but I have seen people chasing the wrong area.

Just download a vibration app for your phone. Note megahz at a given Speed/RPM then convert to cycles per minute and see what is spinning at that speed.

This normally the first step in chasing down a vibration. Back in the day we had to use reed tachs to measure vibration.

 

^That's a great idea, no I have not yet verified.

Had the SS at Speed Inc. today and founds a few things, exhaust leak due to a loose clamp, torque arm bushing housing bent and ripped bushing (these past two could be from my first foray at the strip this week) although the torque arm mount could have been damaged by the trans shop... and they believe the noise I am hearing is coming from the rear-end -- so that will be my next step. Might also look into an aftermarket full-length torque arm now.

Maybe a good time to put different gears in... 3.23 stock in the A4 Vert -- 3.42 or 3.73 -- any inputs?

 

I would get a tunnel mount torque arm or at least a relocation to get the torque arm off the transmission. I would say 3.73s if you don't daily it, it will pick up faster with them.

 

The car is a 13 sec 1/4 car currently, so stock length should be fine. The shorter torque arms have some shortcomings that don't appeal:

short vs long torque arm - LS1TECH

As for gears, the SS is a DD for nice weather, so it has to be good for street use. There is some reason they put 3.23 in the convertible but I am not sure why?! My RS came with 3.42