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ZF launches networked rear axle transmission for SUVs, off-roaders

By Graeme Roberts | 17 October 2018

eLSD rear axle is networked to the vehicle control electronics; software can be updated over-the-air (OTA) from the cloud

eLSD rear axle is networked to the vehicle control electronics; software can be updated over-the-air (OTA) from the cloud

Friedrichshafen, Germany-based Tier 1 supplier ZF claims its new generation of electronic limited slip differential (eLSD) has opened "the next digital chapter for off-road and sports vehicles".

The improved active rear axle drive is based around a newly developed control unit that meets cyber-security standards for software updates from the cloud.

The supplier also has fully networked the limited slip differential with the vehicle's brake system, increasing, it was claimed, both off-road and on-road driving dynamics, stability and comfort.

"The new generation supports a comprehensive, high-quality system network with additional vehicle functions," said ZF project manager Sebastian Dendorfer. "This means that driving conditions can be handled more easily, which leads to advantages in dynamics, safety and comfort."

Space-saving design, more functions

ZF's rear axle transmissions have been used in vehicles produced by major European and American automakers for over 20 years. For the new generation of eLSDs, hardware requirements have been significantly reduced which, in turn, increases the available space for the design of passenger compartments. The supplier has also completely overhauled the electronic control unit (ECU).

Thanks to a new chip set, the ECU supports over the air updates, allowing vehicle software to be updated via the cloud with the most current cyber-security standards protecting the update process. Additional interfaces, such as the CAN with flexible data-rate (CAN FD) now allow for a connection between the eLSD and the integrated brake control system (IBC). This allows for close interaction between drive and brakes. The result is better traction and oversteer protection as well as increased stability when towing or during lane changes.

Off-road, the eLSD plays to its advantage, particularly when climbing hills, while the active limited slip differential helps to improve vehicle control during acceleration and µ-split braking. Improved modulated automatic braking and avoidance of high engine revving at traction manoeuvres make for greater comfort.

The eLSD system features a potential locking torque of up to 3,000Nm and is also suitable for heavy vehicles and high-performance engines. Thanks to its modular principle, the eLSD is both compatible with different final drive ratios as well as different axle drive sizes.