I hope this is a wheel bearing problem or I'm up for a new transmission. So last night I am driving home and hear a whirring noise, I'm losing and gaining power on acceleration and I can feel a rough vibration from the shifter. I slow down because the feeling scares the **** out of me and so I don't want to drive any faster if it will mess up the car especially with bad roads coming up.
I slow down to see if any belts are hanging around if anything is leaking but I see nothing. I start my way back home again and the dreadful sound is still there. And as I hit 15mph the car bucks. Only at around 15mph-20mph the car bucks once.
The car does not make any sound when the gas is not stepped on.
I am truly hoping that is the wheel bearing because I have hit some potholes the past week due to uncareful driving, you know when people keep talking to you in the car and you tell them to shut up. I will be towing her to my shop tomorrow morning but I was hoping anyone could provide some input because I am scared shitless if this is a transmission issue.

 

So, WHAT was it? My guess would actually be the tranny, but, truthfully I've had that sort of issue with any of teh AWD cars I've owned over teh years (Opel & Audi). I'm curious as to what the diagnosis is/was.

 

There are TSB's for both the transmission and wheel bearings on the 04+ A8.
The wheel bearing however has problems with grinding and making a thud noise while turning the wheel to the locks.
The transmission sounds more like what you have, heavy grinding and bucking between gears.
I would guess you need a transmission.