page_title: Quattro (four-wheel-drive system)
section_title: Crown-wheel centre differential
hierarchical_section_title: Quattro (four-wheel-drive system) / Longitudinal systems / Crown-wheel centre differential
caption_attribution_description: English: Audi Media Image of the Audi Crown gear Differential. Use approved by email from Audi Русский: Центральный дифференциал на основе плоских зубчатых колес системы Audi quattro
context_page_description: quattro is the sub-brand used by the car brand Audi to indicate that all-wheel drive technologies or systems are used on specific models of its Audi automobiles.
  The word "quattro" is a registered trademark of Audi AG, a subsidiary of the German automotive concern, Volkswagen Group.
  Quattro was first introduced in 1980 on the permanent four-wheel drive Audi Quattro model, often referred to as the Ur-Quattro. The term quattro has since been applied to all subsequent Audi AWD models. Due to the nomenclature rights derived from the trademark, the word quattro is now always spelled with a lower case "q", in honour of its former namesake.
  Other companies in the Volkswagen Group have used different trademarks for their 4WD vehicles. While Audi has always used the term "quattro", Volkswagen-branded cars initially used "syncro", but more recently, VW uses "4motion". Škoda simply uses the nomenclature "4x4" after the model name, whereas SEAT uses merely "4". None of the above trademarks or nomenclatures defines the operation or type of 4WD system, as detailed below.
context_section_description: Audi debuted a new generation of quattro in the 2010 RS5. The key change is the replacement of the Torsen Type "C" centre differential with an Audi-developed "Crown Gear" differential. Whilst this is superficially the same as a normal Open differential, adapted for a centre application, it has some key differences:
  The central carrier and associated spider gears interface directly to two crown wheels connected to the front and rear drive shafts
  The two crown wheels interface to the spider gears at different diameters, and so produce different torque when turned by the spider gears. This is engineered to produce a 40:60 static torque split front and rear.
  Each crown wheel interfaces to the respective output shaft directly, whilst the spider carrier interfaces to each output shaft using a clutch pack which gives the unit the ability to control torque distribution over and above the static torque distribution.
  If one axle loses grip, different rotational speeds arise inside the differential which result in an increase in axial forces that force the clutch plates to close. Once closed, the output shaft is locked resulting in the diversion of the majority of the torque to the axle achieving better traction. In the Crown Gear differential up to 85% of torque can flow to the rear, and up to 70% of torque can be diverted to the front axle.
  The features of the Crown Gear differential provide the following benefits over the Torsen Type "C"
  The ability to set up a more stable torque distribution, with full locking whereas the Torsen can only provide a torque distribution up to the Torque Bias Ratio; i.e., the Crown Gear differential can lock fully, regardless of bias ratio.  Unlike the Torsen, the Crown Gear differential doesn't operate like a limited slip differential and can operate, fully locked, with no traction on one output shaft.
  Easier integration into control electronics allowing four-wheel electronic torque vectoring with or without the active rear sport differential
  Considerable reduction in size and weight (at 4.8 kg, some 2 kg lighter than the Torsen Type C)
  The net result of this advance in quattro is the ability of the vehicle electronics to fully manage the vehicle dynamics in all traction situations, whether in cornering, acceleration or braking or in any combination of these.
caption: Audi quattro Crown Gear centre differential
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