Get your semi truck Ready for the Road Aheadâ„¢ with enhanced differential protection, with the Spicer 3.819" Differential Pinion Seal and Nut Kit. By utilizing a pin-like design, this replacement bolt is able to keep lubricant inside a differential's housing, while preventing outside contaminants from entering. Crafted with super-strong flour elastomer materials to withstand large amounts of torque and pressure.