Despite a still hesitant start, winter is here. This means of course we can brace ourselves for those strenuous drives at sub-zero temperatures. Faced with ice, snow and generally unpredictable road conditions, a growing number of motorists would like four-wheel drive. However, by no means do all carmakers offer four-wheel drive in their high-volume models. Not so at Volkswagen, where four-wheel drive has now been available in the Golf for 20 years. Besides this current example, Volkswagen also supplies four-wheel drive (4MOTION) in the Passat, Sharan, Touareg and Phaeton, plus the Multivan, Caravelle and Transporter.
- 1986: the Golf syncro brings four-wheel drive to the compact class
- Volkswagens with four-wheel drive: Golf, Passat, Sharan, Multivan, Touareg, Phaeton
- Stress-free winter motoring: Volkswagen’s 4MOTION four-wheel drive offers extra safety
syncro in the Golf
Taking a brief look back, the first four-wheel-drive version of the Golf came out in 1986. As it had so often done before, Volkswagen made a new technology available to a wider public. The Golf syncro gave many motorists their first opportunity to own an affordable car with optimum traction even under difficult road conditions.
syncro in the Passat and Transporter
The four-wheel-drive Passat Estate GT syncro had already been launched two years before. The system’s central differential compensated for wheel speed differences between the front and rear axles when cornering. On slippery ground the differential could be locked to ensure optimum traction at both axles.
However, this was also the most costly form of four-wheel drive system; to build a Golf syncro at a marketable price, a different engineering solution would have to be found. Fortunately, Volkswagen had developed a technology for the four-wheel-drive Transporter, launched in 1985, which suited the Golf perfectly: the viscous coupling. It connected the Golf’s substantially unmodified front-wheel drive with the differential of the syncro rear axle and worked fully automatically without the need for any intervention by the driver. The silicon liquid in the viscous coupling allowed the front and rear axles to turn at different speeds when passing through bends. And when necessary, for instance if the front wheels were standing on sheer ice, it transmitted virtually 100 percent of the engine power to the rear axle.
The same engineering principle was later adopted for the front-engine Transporter T4 and the third-generation Golf. The career of the viscous coupling continued until the introduction of extremely fast reacting electronic vehicle dynamics control systems, such as ESP in the Golf IV; at the same time, the name syncro disappeared from the vehicle ID plates.
4MOTION for the Golf, Passat, Sharan and Multivan
Syncro made way for a new system with a new name: 4MOTION. The Golf Europe’s most successful compact car shares this technology with the Passat, Sharan plus the Multivan and its close technical relatives, the Caravelle and Transporter.
In all of these models an electronically controlled Haldex coupling makes the connection between the front-wheel drive and the rear axle. Its core elements are a multi-plate clutch and an annular piston oil pump. At the slightest difference between the speeds of rotation of the driven front axle and the rear axle, the oil pump produces pressure, closing the multi-plate clutch and the rear wheels instantly receive power. At the same time, the ESP’s control electronics monitor the Haldex coupling. When there are signs that the vehicle is losing directional stability, ESP opens a control valve between the oil pump and the multi-plate clutch, thus interrupting the connection between front and rear axles. ESP can then brake each wheel independently of the others to prevent the vehicle from breaking away.
The electronics also detect when the vehicle is being manoeuvred at low speed and open the control valve accordingly. Otherwise the Haldex coupling would react as soon as the vehicle is manoeuvred with the steering at full lock. This would lead to wind-up in the drivetrain, eventually causing increased tyre wear. But that is not all the control valve does: it also directs the transmission of torque by the Haldex coupling. This takes into account that in some situations it is counterproductive to supply the maximum possible torque to the rear axle, as this could make the vehicle oversteer. The electronics manage the control valve, adjusting the characteristics of the Haldex coupling to help ensure the Volkswagen handles as the driver expects.
4XMOTION for the Touareg
A modified version of the multi-plate clutch is also used the Touareg. The difference in the latest version of Volkswagen’s off-roader is that the rear wheels are driven not only when the front wheels slip; instead, four-wheel drive is permanently active. In this case the system is called 4XMOTION. It is a four-wheel drive system using a transfer box with switchable off-road reduction gearing and a locking central differential as standard. Its electronically controlled multi-plate lock and the rear axle differential (locking as an option) are automatically managed by the running gear electronics. Under normal conditions the torque is distributed 50:50. Depending on the driving situation, the full engine power can be transmitted variably up to 100 percent to just one of the drive axles. A rotary control switch in the cockpit can be used to activate the differential locks manually (100 percent). An electronic differential lock (EDL) governing the power to all four wheels provides fine adjustment of the torque distribution.
4MOTION for the Phaeton
In Volkswagen’s large saloon a Torsen differential, which responds to the slightest differences in axle rotation speed, carries out the key function in distributing engine torque. The 4MOTION system fitted as standard in the Phaeton makes it a genuine four-wheel-drive saloon due to this integrated differential and the standard torque distribution of 50:50 between the front and rear axles.
In this way, the 4MOTION name stands for tailored technology systems engineered to perfectly match each set of a requirements. They all offer major gains in performance and active safety both on dry and on wet or icy ground – letting drivers look forward to a winter’s motoring.