True-Trac limited slip for 83 and newer Ford 10.25" and 10.5" with 35 spline axles. The True Trac limited slip uses a worm-gear design to bias torque from one tire to the other, providing extremely smooth operation. Since there are no clutches in this unit, there are no parts to wear out and no need to run limited slip additive in your oil. Tractech warranties this unit for one year against manufacturing defect.