Need help with codes on a 03 A6 2.7T

[CHGOA6]

Hey guys, I'm hoping one of you guys can help me out here. I have a 03 Audi A6 2.7T and about 2 months ago it went into safe mode. I was almost 100% sure it was the trans since it had been slipping on me previously. So I had a mechanic come out and take a look at it but that was all he did, he didn't connect the car to run diagnostics he just looked at it and said it needed a new trans. At the time I didn't have enough for the situation but I saved up and now I finally have enough. My mechanic that changed my alternator for 120$ was wiling to rebuild it and install for 2500$ OR if I got ahold of another transmission he would take out the old one and install the new one for 500$. Obviously I chose the cheaper option and I finally found the right transmission (trans code FAQ) but the thing was that it was in Ohio and I'm in Chicago. He was asking 900 but he lowered it to 500 if I could make it out there this weekend. It has 91000 miles and is shrink wrapped from the place he bought it from but never used. So I wanted to make sure that it was the trans before I bought it and I also wanted to see if I had any other codes to estimate how much it would cost to fix. Yesterday I had a mechanic run a diagnostic and these are the codes he got back.

TRANS codes

17125: torque converter clutch stuck OFF/no power being transferred P0741

17114: Gear ratio monitoring incorrect gear ratio P0730

17195: Excessive clutch slippage P0811

18161:Tiptronic switch (F189) implausible signal P1753 intermittent

ENGINE codes

16684: Random/Multiple cylinder misfire detected P0300 intermittent

16687: Cylinder 3 Misfire detected P0303 intermittent

17687:Brake boost vacuum system mechanical malfunction

So I know I need the trans but do I also need a new torque converter? What about engine code wise? Thanks a lot for reading thru

[crazyquik22023]

From the codes it seems like you need a new torque convertor and possibly a new tiptronic switch. The switch might be misaligned too causing the 18161 code. Sometimes the 17114 code can pop up if your low on transmission fluid. It's hard to say without seeing the car if you need a new transmission or not. As for the engine codes you probably have a vacuum leak and/or a bad coil pack on cylinder 3. Check the wiring of the coil before you buy a new one. Also check the condition of the spark plugs as well.

[CHGOA6]

Thanks, right before it went into safe mode the car wouldn't move forward without alot of RPMs but the reverse worked fine, and then altogether it stopped reversing too. Thats pretty much why im assuming that it has to be the trans

[CHGOA6]

Anyone else have any insight on this?