The car has been doing this since i purchased it, hasn't got any worse or feels any different after about 12k miles of driving. Basically what happens is when i'm cruising at 60 mph in traffic as i approach slowing traffic i'll downshift to 4th as i let the car engine brake traffic starts to move so i'll apply the gas in the first second as the car moves from engine brake to pushing its own weight i feel a shutter of some kind, kinda like a bad trans mount motor mount something. Upon looking at my engine mounts the L and R sides are leaking a little fluid but still look fine, and besides i dont feel and excessive amount of vibration car idles and rides real smooth. The front mount is a little dry rotted but still looks ok. The only one i really couldn't see or check was the diff mount, from looking at ecstuning theres a bushing that they advertise reduces slack in the drivetrain is this the bushing that is causing my shutter?

Audi B6 A4 Quattro 1.8T > Drivetrain > Mounts > ES#4665 Snub Mount - ECS#137

 

Once the mounts leak they are pretty well shot. And they really have little fluid to start with.

 

At this time i dont want to change them if they're not the root cause of my problem. It's coming from the rear anyways and i feel no front end vibration. No sense in changing them at this point.

 

I'm pretty sure i've located the problem but i wanted a second opinion before i drop the driveshaft.

 

Can no one put light on the situation? Since i've joined this forum i haven't found any useful information.. If have a question on how to install brake pads or putting oil in the car i'll make sure i ask here. lol