[Regulus]

The Jeep Grand Cherokee zj also have the *hopping* in low speed tight turns.
So I wouldn't even notice if the Audi does it. All normal 4x4 behaviour in my mind.

I had to replace my -98s diff 1.5 years ago. The viscous coupling was broken.
When it got warm, say after a 20 mins drive. It would start to lock up in roundabouts. And I mean real lock up, where you feel the car twist.
In my case it was probably my own fault. Doing the service on the car myself for years, but never realising the diff in that car is separate from the gearbox. I learned the hard way that car needs diff oil change too.