As Audi's video shows, Torsen differential is used between the rear and front axle for A4 Quattro.

Anyone knows what kind of differential is used between left/right wheels? Torsen again or just a normal open differential?

 

Audi > Glossary > Engine & Driveline > Electronic differential lock (EDL)

Torsen for centre diff with longitudinal engines only; front & rear differentials are electronic; A3 & TT use a Haldex centre differential

 

The EDL should work on the brakes to deal with wheel spin. However, there must be some sort of differential gear between the left/rigt rear wheels under normal steer/turn. I guess it is a open differential, just want to see if someone can confirm that.

 

Yes apart from the braking functions it is an open differential.

All Wheel Drive Encyclopedia | AWD.EE - 4x4, 4wd, 4motion, quattro, xDrive, SH-AWD, Haldex, Torsen - How it works. This link has some interesting videos on how EDL works,

 

thanks for refering the site. It list out all the rear/front/central differential types used in various quattro generations.

"http://www.awd.ee/quattro.html"

Thanks.