In its present form, the purely mechanical system sends 60 percent of the engine’s power to the rear wheels under normal driving conditions. In abnormal conditions, the A4’s self-locking center differential redirects that power to the axle with the best traction.
This is the best-handling A4 we’ve ever tested. Its slalom speed of 70 mph and 0.86g skid pad performance essentially match the numbers of the Audi RS 4.
Source: Inside Line