After years of research and development, we are proud to release our JHM Helical Rear Limited Slip Differential (LSD) for the B6-B7 A4 and B6-B7 S4. In the stock Audi rear differential, the torque from the motor that's sent to the driveline is evenly divided between the two rear axles. In most driving situations this is normally fine. However, in cases where traction is lost at one wheel (i.e. under hard acceleration out of a corner or launching from a stop) power is only being sent to the spinning wheel. In these situations, a gear-based limited slip differential will take the torque from the wheel that's starting to spin and send it back to the wheel with that's not - the one with better traction. This means that both rear tires will spin together - with or without traction. Features and Benefits of the JHM Helical LSD: - Helical gears respond to changes in traction conditions very quickly - Improves traction and predictability of vehicle behavior: both rear wheels will spin at the same rate. Under hard acceleration out of corners or launching from a stop the car will either "hook up" and go or both rear tires will spin. Some "track focused" drivers say that this allows you to steer the car better with the throttle. - Prevents "one-legging" (spinning one rear tire only) and therefore eliminates losses in acceleration under load out of corners and heavy acceleration from a stop (launching). - Maintenance free! There are no clutch packs to replace as they wear out. - No special gear oil or additives necessary. Again, since there are no clutches, you can run the same gear oil as recommended by Audi in our LSD. JHM Limited Slip Differential (LSD) Product Page: http://jhmotorsports.com/shop/catalog/advanced_search_result.php?keywords=JHM+LSD&x=0&y=0