The idea was simple enough: Transfer power from front to back and side to side as needed. After all, a wheel spinning is wasted motion. Along with better performance, quattro® provides high levels of active safety and improved traction on virtually all surfaces. On cars with longitudinally installed engines, a differential distributes power and compensates for differences in wheel rotation when cornering; if the car has a transverse engine, these tasks are performed by a Haldex® clutch.