i have a 2001 S3.
after reading loads of posts ive relised that the 4wheel drive system has loads of issues mine being one of them as it turns out.
after following some posts i noticed my earth strap is broken so i fixed this and still no joy. i then checked the plug for corrosion and it looked like new. what i have now spotted under the car is a plug that was disconnected near a blue thing. i plugged it back in and reversed in a straight line and it was fine. 1st turn that i did , it didnt sound to good. its like it was juddering but the wheels moved freely enough for it to drive. so straight lines are fine but any corners it judders.
any advice on what to check or replace next ?