I had no problem with my2000 A6 2.7T until I brought in for the 60K mile scheduled maintenance. The dealer found that there was a leak in the drive shaft seal and replaced it. One week later the check engine light turned on and I got the error code 17125 - Torque Converter Clutch: Stuck OFF / No Power being transferred P0741 - 35-00. The dealer recommended to replace the torque converter, but the shop where I took the car for the smog check told me that replacing the torque converter will not fix the problem because the cause is a solenoid in the transmission and recommended replacing the transmission. I did some testing using VAC-COM software and I found 2 Faults:
17125 - Torque Converter Clutch: Stuck OFF / No Power being transferred
P0741 - 35-00 - -
18238 - Pressure Control Valve 4 (N218): Short to Plus
P1830 - 35-10 - - - Intermittent
Is it possible to fix the pressure control valve without replacing the entire transmission?
Is it safe to drive the car with a faulty Control Valve?
Except for the annoying check engine light the car drive fine.

 

You do need a new torque converter, but you can replace a shift solinoid. Its not a common problem to fail however so i would try to erase all the faults and see if any of them come back.
The dealer would have to order the shift solinoid if it needed one.

 

ill add my .02$ ... whoever told you that you needed to replace the whole trans is most likely unknowledgable ... clear the faults with vagcom and see what comes back (ahhh the beauty of vagcom) this will save you oney and unnessecary repairs .. im sure auditech79 is way more knowledgable then myself but it may be something else that is much more minor then replacing the entire transmission ... with around 60k miles on an 00 the trans should not need entire replacement!!

 

It could be low in transmission oil too.