WARNING: This page is about a different car, the 2005 Audi A4, 2004 Audi A4, 2003 Audi A4, and 2002 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Inspect Torque Converter Hub For Irregular Grooves
Courtesy of VOLKSWAGEN UNITED STATES, INC.
Checking converter hub for wear grooves (arrow).
NOTE:
The torque converter is welded in and must be completely replaced if damaged or in case of malfunctions.