Caterpillar Inc. 5P-8403 O-Ring

Caterpillar 5P-8403 is an OEM toric O-ring seal designed specifically for Caterpillar service brake assemblies that use a Duo Cone sealing configuration in hydraulic brake circuits. Cat documents label this part as a “Duo Cone Toric Sealing Ring,” and it is sold as a genuine replacement under part number 5P-8403 to ensure a correct fit and reliable sealing in the brake system. The seal is compatible with multiple Cat machines, including models 772B, 773B, 775B, 776, 776B, 777, 777B, 784B, and 785, providing a factory-fit option when servicing the brake system and minimizing compatibility concerns during maintenance. As an authentic Cat O-ring, 5P-8403 serves as the critical fluid seal within the Duo Cone brake arrangement, helping prevent leaks and maintain brake performance under typical operating pressures and temperatures encountered on Cat equipment. O-rings of this style seal gaps between mating brake components under hydraulic pressure, and the Duo Cone toric geometry is designed to distribute compression across multiple surfaces for improved reliability in demanding service brake applications.