DESCRIPTION DESCRIPTION: The Yukon Dura Grip uses a nodular case and forged 4320 internals for added strength along with composite clutches for high performance and long life. All units are Rebuildable and many offer upgrades to increase aggressiveness for racing applications. Each unit carries a one year warranty against defects. ***Will not fit F150’s with the HD max tow package! 9.75C as they have 35-spline axles. DETAILS DETAILS: Fits Ford 9.75"34 spline axles4-spring\, clutch style positractionInternal gears are manufactured using forged 4320 steel and cut to provide stronger teethFully rebuildableAssembled in the USA Technical Notes: Yukon recommends the use of high grade GL-5 gear oil and two bottles of Yukon LSD (Limited Slip Differential) additive for long life and smooth operation. Part number OILADD. The use of synthetic oil is allowed but may result in aggressive or noisy operation.