THE B4 employs a viscous coupling limited slip centre differential (LSD) to transmit engine power to all four wheels. In normal conditions this system operates with a 50/50 torque split between the front and rear axles, but the viscous LSD automatically adjusts the torque distribution dependent on load distribution and tyre grip - such as during unstable driving conditions, like on slippery surfaces or under hard acceleration. The B4 also uses an LSD on the rear axle to enable the transfer of power between the rear wheels depending on available traction.