4MOTION® Haldex System
The Haldex Differential
The Volkswagen 4MOTION all-wheel drive system is a key technology in sporty, but above all safe driving. At the core of this method of power transmission to all four wheels is the Haldex coupling. The Haldex coupling is mounted in front of the rear axle differential and actually becomes part of the rear differential case. Yet, it functions as a center differential. Its hydraulic and electronic systems automatically detect wheel slippage (for example, due to road conditions or high power requirements) and distribute the tractive force to the two axles accordingly.
And because it‘s so fast in slip detection, in the absence of wheel slippage, this system defaults to front-wheel drive for better fuel economy and less wear on the drive train. When driving the Golf R32, you hardly notice the work of the 4MOTION Haldex system. You only feel the absence of under- and oversteering. Even on wet roads or when accelerating quickly out of tight curves, there is no noticeable wheel slip, and extreme spurts do not cause the steering to jerk. In addition you do not feel any wind-up in the drive train when maneuvering into tight parking spaces.
The development of the Haldex differential is a giant step forward in modern all-wheel-drive technology. It is controlled based on the inputs the Haldex control module receives from the vehicle. 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 module for data that provides the processor with all the information it needs. This information includes road speed, cornering, and coasting or traction mode — all of which allow the Haldex system to respond optimally to any driving situation.
The Haldex system is also used on the European Golf and Bora 4MOTION, Audi A3 and TT Quattro, and other vehicles.
How it works
The Haldex center differential is mounted on the rear axle differential and is driven by the prop shaft.
Engine torque is transmitted through the gearbox to the prop shaft.
The prop shaft is connected to the input shaft of the Haldex differential. In the Haldex differential, the input shaft is separated from the output shaft to the rear axle differential. Torque can only be transmitted to the rear axle differential when the Haldex differential clutch plates are engaged.
In the absence of wheel slippage, the clutch plates are not engaged, and only front-wheel drive operates until power is needed for the rear axle.
The Advantages
The 4MOTION Haldex system results in the following advantages:
- Permanent all-wheel drive with electronically controlled multi-plate clutch
- Front drive characteristic (distributes power to the rear axle only when needed)
- Quick response time
- No strain on clutch when parking and maneuvering the vehicle
- Compatible with different tires (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