X-Drive is BMW's trademarked name for the all-wheel drive system used on the X5, X6, X3, 3, 5 Series and other future series. Its latest generation employs a multi-plate clutch transfer box situated between the axes to direct the power split between front and rear wheels.
Not depending on the ABS sensors alone, like the previous generation, the X-Drive is now controlled by a central ECU which transformed the system from a reactive to an active one. In other words, if just one of the wheels starts slipping the ABS sensors detect it and send the gathered data to the ECU which in turn commands the wet multi-plate clutch trough a high speed electric servo-motor which turns an actuator shaped like a disc.
In normal driving mode, the system splits the torque with a 38% - 62% distribution ration between the front and rear axles, but depending on driving conditions it can send up to 100% to a single axle.
X-Drive all-wheel drive system
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