Multiquip 178401000 Locknut 3/4"-16

The Multiquip 178401000 Locknut 3/4"-16 is a genuine OEM fastener designed for MQD2H and MQD3H diaphragm pumps. This is the factory-specified locking nut used to secure critical pump components, ensuring correct torque retention and resistance to vibration-induced loosening during operation. Sourced directly from Multiquip, part number 178401000 matches the exact thread pitch and dimensional spec required for a correct installation on compatible MQD series equipment.

Key Features

• Genuine OEM Thread Specification — Factory-correct 3/4"-16 thread pitch ensures proper engagement and full clamping load without risk of cross-threading or premature wear.
• Vibration-Resistant Locking Design — Built to maintain clamping force under the continuous vibration generated during pump operation, preventing fastener back-out in service.
• Direct-Fit for MQD Series Pumps — Confirmed fitment for MQD2H and MQD3H diaphragm pumps; installs in place of the original hardware without modification.
• Maintains Structural Integrity — A correctly torqued locknut keeps pump assemblies secure and aligned; a loose or incorrect fastener can lead to component shift, leaks, or accelerated wear on surrounding parts.
• Backed by Multiquip OEM Supply Chain — Sold as a genuine Multiquip replacement, so you get the same hardware the pump was built with — no guesswork on grade or dimensions.

A locknut is a fastener engineered to resist loosening under vibration and dynamic loads. Unlike a standard hex nut, a locknut incorporates a locking feature — such as a distorted thread or nylon insert — that creates resistance against rotation once torqued into position. On diaphragm pumps like the MQD2H and MQD3H, where cyclic pressure pulses and mechanical vibration are constant, maintaining fastener security is essential to keeping pump assemblies properly clamped and leak-free. When a locknut fails, stretches, or is replaced with an incorrect grade or thread pitch, it can allow critical components to shift, resulting in misalignment, fluid leaks, or damage to mating parts.

Have questions about fitment or need help confirming this is the right part for your equipment? Contact the DHS Equipment parts team for assistance.

Part Details

Compatibility & Fitment

Verify Before You Order

Fitment is machine-number and revision-specific; always confirm your model and serial number against the fitment list.

Why Buy From DHS Equipment

Every part is verified against the manufacturer's part number before it ships, so what you order is what arrives. We carry parts from leading OEM brands and our own DHS Quality Parts line of professional aftermarket components. Need help finding the right part? Our team is available to confirm compatibility whenever you need it. Orders are processed fast to keep your jobs on track. We don't just sell parts. We keep you jobsite ready.

Questions? Contact our team at [email protected] or 866-611-9369 — DHS Equipment is here to help you maintain peak performance.