The front and rear final drives are conventional "open" differentials (ratio 3.317) and use the Audi "Electronic Differential Lock" (EDL). EDL is a part, or "function", of the Bosch ESP 8.0 Electronic Stability Programme, which also includes "Anti-Slip Regulation" (ASR) traction control system. EDL does not 'lock' the differential in a traditional sense, but uses electronics to compare the speeds of the two wheels on an axle, and brakes any wheel that is sensed to have lost traction (by rotating faster than the opposite wheel, beyond normally accepted deviations). This braking of a slipping wheel has the effect of transferring torque across the axle to the other wheel, which is assumed still to have traction.