2001
The second generation of Haldex coupling is an electronically controlled permanent 4x4 system with a Haldex differential calculating how much drive should be directed to the rear wheels. The Haldex system automatically distributes power between the front and rear wheels depending on slippage, but normally sends 95% of the power to the front wheels. It can react in as little as one seventh of a revolution of any wheel. Power transfer in the second generation is much more effective. Electronic sensors and controls can modify the system's response characteristics, for better operation in conditions ranging from dry pavement to loose gravel, snow, ice, or mud. A pre-charge pump charges the hydraulic system to allow the coupling to engage quickly. This pump was improved for the third generation to allow for greater speed.
Read more about this topic: Haldex Traction, Second Generation