Originally Posted by superswiss

Not unless you speak German. My source is Audi Germany. It's even stated on audi.de that the B9 A4 uses the planetary gear self-locking center differential.

Just a comment on Glisse's post. No current S5 uses the planetary gear set self-locking center differential. The 6MT S5 has the old torsen center diff and the B8.5 S-tronic S5 has the crown-gear self-locking diff. In my experience there is a major difference in driving dynamics between the old torsen and the new self-locking diffs with torque-vectoring, so I don't agree with your assessment. I would never go back to a Quattro with the old torsen diff.

Here's more info on the planetary-gear self-locking center differential. This is not the torsen diff. The torsen works on a different principal.

Self-locking center differential ? Audi Technology Portal

EDIT: Didn't have the link handy anymore. If you do speak German, here's all the info about the A4's powertrain directly from the Audi Germany website. I trust this much more than some blogger that probably mistranslated German information into English.

Motoren und Antrieb > A4 Limousine > A4 > Audi Deutschland