3398-W888
Locknut, 5/8-18
Mack

The Locknut, 5/8-18 provides a secure fastening solution for components exposed to vibration and dynamic loads in heavy-duty environments. This steel locknut features the standard 5/8-18 thread size and a robust outer profile designed to resist loosening during harsh driving conditions. The body is typically coated or plated to resist corrosion from road salts and moisture, extending service life in exposed chassis and driveline assemblies. Used in conjunction with washers and compatible studs, this nut helps maintain accurate preloads and joint integrity, contributing to reliable suspension mounts, brackets, and driveline connections. Precise threading ensures a dependable bite and consistent torque retention, which is crucial for maintaining alignment and reducing maintenance cycles. Proper installation—tightened to the recommended specification and inspected for wear at routine service—will maximize joint security and system performance. When replacing, consider inspecting related fasteners for compatibility and cross-threading indicators. Source One Parts Center