Quattro

[PussyCat]

quattro is Audis trademarked name for their four-wheel drive system. Now at its fifth generation since it was introduced in 1980 (on the Quattro model, or Ur-Quattro as it is known), the quattro all-wheel drive system is a permanent one, without the possibility of switching from four to two wheel drive.
Since on most of Audis vehicles since the 80s it was designed around a Torsen (torque-sensing) central differential, in case of grip loss on certain road surfaces it can distribute torque between front and rear axles depending on the grip level.