Self Study Program 206 – Four-Wheel Drive with Haldex Coupling

VAG SSP 206. Volkswagen and Audi have been building permanent four-wheel drive systems for almost 15 years. In Volkswagen’s system, a viscous coupling distributes input torque to the rear axle; in Audi’s system this job is performed by a Torsen differential. The slip-recognising system is activated by a difference in speeds between the front and rear axles. Once activated, it distributes input torque to both axles.

The viscous coupling previously used by Volkswagen was able to detect slip alone, but not the cause of it.

The development of the Haldex coupling is a giant step forward in modern four-wheel-drive technology. The Haldex coupling is controllable.

A processor also makes allowance for additional information during the control process. Slip is no longer the only decisive factor in the distribution of drive forces; the car’s dynamic state is also a factor. The processor accesses the ABS wheel speed sensors and the engine control unit (accelerator pedal signal) via the CAN bus.

This data provides the processor with all the information it needs on road speed, cornering, overrun or traction mode, and can respond optimally to any driving situation.

Advantages of the Haldex coupling

  • Permanent four-wheel drive with electronically controlled multi-plate clutch
  • Front drive characteristic
  • Quick response
  • No strain on clutch when parking and manoeuvring vehicle
  • Compatible with different tyres (e.g. emergency wheel)
  • No restrictions on towing with the axle raised off the ground
  • Fully combinable with traction control systems such as ABS, EDL, TCS, EBD and ESP


  • Four-wheel drive
  • Haldex coupling
  • Mechanicals
  • Hydraulics
  • Test your knowledge
  • System overview
  • Electrics
  • Driving situations
  • Function diagram
  • Self-diagnosis
  • Test your knowledge

The Self-Study Programme is not a Workshop Manual.
Please always refer to the relevant Service Literature for all inspection, adjustment and repair instructions.

Language: English
Format: PDF
Pages: 44

Self Study Program 206 – Four-Wheel Drive with Haldex Coupling Design and Function PDF free online