'98 A8 quattro Transmission Issues (I think)
 

So this is probably the 10000th thread about A8 D2 transmission issues, but I couldn't find any other thread describing the exact issues I'm experiencing... I went to reverse out of my parking space, and I got about one foot before the car suddenly stopped and it almost felt like I had hit something, when I put it back into drive it did the same thing, went about a foot before suddenly stopping entirely... after giving it a fair amount of accelleration, it'll move forwards or backwards again, but with a constant sort-of grinding noise, it sounds like when I brake (because my rear brake pads are completely gone and I'm just grinding against the rotors now).

What could it be? Trying to pull transmission codes from VAG resulted in zero fault codes on the transmission... where should I start with trying to fix this? I'm nervous to try and drive it anywhere, in fear of causing more serious damage to something, but is it safe to drive? If I were to drive in manual mode, in second gear or something? Should I recode the transmission to 00012? Please, any help is much appreciated, this is my only car and I'm just a poor college student so I don't have a huge budget to have someone repair it, so any repairs I could possibly do myself is ideal... and in the meantime I have zero transportation, which makes going to work much more difficult, so I need to get this fixed ASAP.

You sure it's NOT brakes? Put it in neutral and see if you can roll it back and forth a few feet just to make sure you don't have a caliper completely binding up.

the odd thing about the transmission theory is, if it's really binding up like that, it should absolutely throw you into LIMP mode with all the gear positions on the cluster lit up.

If it rolls OK, then I'd pull the transmission codes next.

Hahah I feel dumb now, I just had a tow truck come out a little bit ago to tow it to a repair place and when I was backing my car up the guy immediately said "that's your rear brakes"

Thank god it's not an issue with my transmission I'm so relieved! I just hit 150k miles so I'm terrified of experiencing the dreaded transmission issues haha, I also feel stupid for waiting this long to get my brake pads replaced, to the point where the car literally wouldn't drive anymore, I honestly didn't even realize that was a possibility with bad brakes

Well, that's less expensive than the transmission...

I'd view it as a chance to do a complete replacement on calipers, pads and rotors back there. I think the parking brake scheme's a little wonky on these, as I've had three D2s over the years start dragging calipers back there. No wheel fires, fortunately, but it happens more than it should...

Thanks for the advice! Is that something that's possible to do on my own or should I just let the repair shop take care of all of that??

I had one rear caliper get sticky such that it hung up every time I used the parking brake, I had to knock it loose again or it'd drag. However your car sounds like it has more brake pressure than this.
Replacing the calipers is straightforward, it's more work than a simple brake job but a reasonable shadetree project.

If you are worried about the transmission (as you should be) you should apply the fix to it so it does not destroy itself. Search up the TransGo 5hp24 kit, there are threads here and on another popular D2 forum. You have to perform this before the trans misbehaves and blows a clutch seal or breaks a drum. One of my cars had enough wear to the lower valve body I replaced that casting as well. $150, but money well spent now that it's sorted out. Maybe $325 all-in for the Transgo Valve, the casting, gasket, filter, and fluid but that's not much compared to $4K-$5K for a transmission rebuild or on many cases scrapping the car instead.

Caliper bolts on with only two bolts IIRC. I think a 13 mm and 15 mm wrench are all that's required once it's up on jackstands with wheel off.
The rotor's a bit tougher, but the biggie is needing to re-bleed the brake circuit.

It's tougher than an oil change, but lots of us have done them at home.