Soft-roader All-Wheel Drive Systems: A Few Simple Truths

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- Andrew Middleton

When it comes to adding drive to the rear axles of most soft-roaders, there is plenty of jargon out there, but it often boils down to another fancy acronym for much the same thing. It’s easy to be confused by the multiple names used for the same systems, and conversely, one name (such as Volkswagen’s 4Motion) which encompasses a number of variations of a system on different vehicles.

For example, a manufacturer such as Nissan calls the system in their X-Trail and Qashqai ‘All-Mode 4x4’ and uses it in various guises on Alliance cousins such as the Renault Koleos and Duster. They use an electro-magnetically actuated wet clutch pack device developed by GKN Driveline.

If you are looking at a softroader from the VW Group, or from Volvo or Ford, it’s likely to be based on a fluid-activated valve-based wet clutch pack, developed by the Swedish company Haldex-AB (which was bought out by BorgWarner in 2010).

There are also plenty of proprietary systems, with model-specific variations and fine-tuning over time – think BMW’s xDrive and Mercedes-Benz's 4Matic.

Most of these all-wheel drive (AWD) systems were developed to provide a simple, relatively low cost and somewhat less robust alternative to traditional four-wheel drive (4WD), which typically uses a gear-based transfer case and, often, differential locks to send torque to all four corners. AWD systems were developed to supply additional traction to drivelines based on (usually) transverse-mounted engines, where the default drive is to the front wheels. These systems are designed to work in the background with little or no driver engagement.