The POWERTRAX® TRACTION SYSTEMS are the latest design in traction adding differential technology. It combines the smooth operation of a limited-slip differential, with the traction performance of a locking differential. a precise synchronization mechanism eliminates the ratcheting sounds typical of other locking differentials. Special gear and spring design reduce the backlash and therefore driveline windup. Only ultra strength material is used which is 67% stronger than titanium. Installation is simple because no ring and pinion set-up is required. In addition, no special tools or oils are needed. Step by step model specific instructions are provided with every kit. NOTE: POWERTRAX® TRACTION SYSTEMS are designed to intall into "open" type differentials only. They are not designed to replace a locker or positraction unit.Pit Stop USA offers Powertrax No-Slip Traction System - Ford 9" - 31 Spline - 57-87 92-0690-3100 at low everyday prices. Be sure to check out all of our products from PowerTrax Traction Systems including PowerTrax Traction Systems No-Slip Traction System.