Combining all-wheel drive and fuel efficiency

Disconnect technology explained

Conventional all-wheel drive (AWD) systems can be inefficient at times. In most journeys there are periods when AWD is not needed and although the system does not send torque to the rear wheels, all its shafts and gears are still rotating. The inefficiency can account for 2-4% of an AWD vehicle’s fuel bill or CO2 emissions.

What Disconnect does

GKN’s Disconnect all-wheel drive system automatically disengages the main rotating parts in the driveline to reduce losses. When the added performance is needed, the system returns drive to the rear axle, reintroducing the torque smoothly and instantly.

For drivers, it’s reassuring to know their AWD doesn’t just give them more traction when they need it – the system also actively minimizes their environmental footprint.

How Disconnect works

GKN’s development of the industry’s first AWD Disconnect system brought together electronic torque management experts, all-wheel drive designers and software engineers from across GKN’s global development network.

The system combines a specially developed Power Transfer Unit (PTU) with GKN’s Final Drive Unit (FDU) technology. The PTU at the front of the vehicle links to the transmission’s final drive differential. An integrated fast-disconnect device and brake disengages the all-wheel drive system upstream of the PTU’s hypoid gears.

AWD System BSUV

At the rear, either a single electro-magnetically actuated clutch or GKN’s twin-clutch Twinster system disengages the driveline downstream of the hypoid gears. This isolates it from the rotating rear axle to reduce drag losses and as well as enabling the AWD system to bias torque.

A dedicated driveline ECU running GKN software analyses vehicle data to identify steady state driving at speeds of 22mph or more, when it can disengage the PTU and rear differential. When the vehicle’s dynamic demands change, returning torque to the rear wheels occurs in less than 300 milliseconds. An intelligent torque biasing function provides precise control of the front-rear torque distribution, optimising traction, performance and stability.


Global system integrator

Some of the most famous names in all-wheel drive systems, including Range Rover and Jeep, have sourced complete all-wheel disconnect systems from GKN. The system supplied to the Jeep Renegade mini SUV and its sister model the Fiat 500X is the most compact, highly integrated ever produced. GKN’s was responsible for the complete vehicle integration of the system and its localisation, production and delivery in Europe, North America and Asia.

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