Caterpillar 4J-3420 Wear Ring For Hydraulic Cylinder

Cat 4J-3420 Wear Ring, also cataloged as 4J3420, is a piston guide for Caterpillar hydraulic cylinders. The part specifies a 127 mm bore diameter and is designed to serve as a replaceable wear surface inside the cylinder bore to support the piston during travel and help maintain alignment under load. Cat describes this wear ring as a component used to service hydraulic cylinder assemblies to keep equipment leak-free, underscoring its role in preventing metal‑to‑metal contact and preserving smooth piston guidance during operation. Designed specifically for Caterpillar equipment, the 4J-3420 wear ring should be matched to the cylinder bore and part number to ensure a correct fit and function; using the correct bore diameter is essential for proper clearance and reliable cylinder performance. When replacing worn rings, technicians typically verify bore condition and confirm that the replacement bore size aligns with the original specification of 127 mm, ensuring compatibility with Cat hydraulic cylinder configurations that require a 4J-3420 wear ring.