Check out this sticker - what is the part #?
 

Alright, I've created several posts on this issue and it is driving me nuts!! Tranny use to go into limp/safe mode every few days. I replaced the black plastic piece that has the 2 magnets on it b/c VAG-COM shows "transmission relay" issues. I did not replace the circuit board underneath. I did however take a pic of the sticker on the circuit board before reassembly - thinking of replacing that now. The car was fine for a few weeks and is now acting up again. I had to shut off/start the car 6 times this morning so I could leave for work and then the damn thing did it again when I wanted to leave work to come home!!!!

http://www.flickr.com/photos/gonepostal/3876058485/

I think it's the A003809Q, but I'm not finding any info online. Where does everyone order their OEM parts from??

Thats the actual TR (transmission range) switch you are looking at. You won't be able to find that part outside the dealer. The A0028909 Q number isn't the part number exactly, its a number to help the dealer narrow down which one you need. When the dealer pulls up your VIN number it will give him several different switches to choose from, sometimes not.

Alright, thanks for the info. Guess I'll be calling the nearest dealer tomorrow then. I HAVE to get this fixed. Makes me want to do really bad things to the car everytime it messes up. Hopefully they can get the part quick as this weekend is deemed 'A6 weekend' and is full of fun projects like timing belt, front diff changes, etc.

You could try Shokan.com They are an audi only used & new parts supplier/ junk yard.

The guarantee all of their parts and are very knowledgable. I have ordered a few items that only they had after trying numerous other sources.