This Teflon ring seals the interface between the gearbox housing and the rotating shaft in the drivetrain assembly. It sits in a machined groove on the shaft or housing bore, preventing oil leakage from the transmission case while allowing the shaft to rotate freely. A worn or hardened ring allows oil to bypass the seal, leading to a visible drip at the lowest point of the housing and a gradual loss of transmission lubricant. The manufacturer machines this ring to the same cross-section and groove fit as the original component, so it seats without additional shimming or modification. On installation, clean the groove thoroughly and press the ring in evenly to avoid twisting.