Cummins Crank Shaft Damper Hexagon Flange Head Cap Screw Kit

This OEM Cummins Hexagon Flange Head Cap Screw is a genuine OEM fastener designed for use in heavy-duty Cummins diesel engines in the On-Road, Off Road and Marine applications. Engineered to Cummins manufacturing standards, this cap screw provides reliable clamping force, excellent vibration resistance, and long service life in demanding engine applications.

Product Overview

This Cummins OEM cap screw set features The 12 required OEM fasteners with an integrated hexagon flange head, which helps evenly distribute load across the mounting surface and reduces the need for separate washers. The flange head design improves joint stability and helps prevent loosening in high-vibration environments commonly found in heavy-duty diesel engines.

The Cummins 3680750 cap screw set is used primarily on the 15-liter ISX, QSX, and X15 series engines and is intended as a direct replacement for the original factory hardware.

Key Features

• Genuine Cummins OEM fastener
• Hexagon flange head for improved load distribution
• Designed for high-vibration diesel engine environments
• Direct-fit replacement with no modification required
• Manufactured to Cummins quality and durability standards

Applications

• Cummins ISX 15L engines
• Cummins QSX 15L engines
• Cummins X15 engines
• Engine and component assemblies requiring OEM Cummins fasteners

Fitment Note: Always verify compatibility using your engine serial number (ESN) before ordering. If you have any questions about the application of this product please Contact Us with your ESN prior to placing and order for this Non Returnable OEM Cummins Part. 

Replacing the OEM crankshaft damper bolts on a Cummins ISX, QSX or X15 when you install a new viscous crankshaft damper is essential because the bolts are torque‑to‑yield fasteners that lose their engineered clamping force once used. A fresh, high‑performance damper can only work correctly if the hardware securing it can maintain full, reliable clamp load.

Why Cummins ISX QSX X15 Crankshaft Damper Bolts Must Be Replaced

These OEM Cummins crankshaft damper bolts are engineered to stretch when torqued. That stretch is what creates the precise clamping force needed to keep the damper locked to the crankshaft.

Once stretched, they cannot return to their original length, meaning:

• They cannot achieve full clamp load a second time.
• Reusing them risks loosening under vibration.
• Any loss of clamp load allows micro‑movement between the damper and crank snout.

This is the single biggest reason Cummins and professional engine builders treat them as single‑use hardware.

Mechanical Risks of Reusing Old Bolts

• Damper walk — the damper slowly shifts on the crankshaft, throwing off balance.
• Fretting damage — microscopic movement chews into the crank snout and damper hub.
• Premature damper failure — even a premium viscous damper can fail if not clamped correctly.
• Crankshaft damage — severe fretting can require crankshaft replacement.
• Warranty exposure — any damper‑related failure will be blamed on the damper, not the reused bolts.

A complete set replacement bolts protects a $600–$1,000 damper and a $20,000+ engine.

Why It Matters Even More With High‑Performance Viscous Dampers

High‑performance viscous dampers (PDI, Vibratech, Fluidampr, Pittsburgh Power, etc.) are heavier and absorb more torsional energy than stock units. That means:

• Higher inertia loads
• More torsional resistance
• Greater demand on the clamping hardware

Old bolts simply cannot maintain the required preload to keep a performance damper stable under these loads.

Practical and Customer‑Facing Benefits

• Professional best practice — every reputable Cummins builder replaces these bolts.
• Cleaner installation — no guessing about bolt history or stretch.
• Reduced comebacks — eliminates one of the most common causes of damper‑related failures.

Summary of the Cummins Crankshaft Damper Bolt Kit

You replace the bolts because they are single‑use, torque‑to‑yield fasteners, and reusing them risks damper loosening, crankshaft damage, and premature failure of even the best viscous damper. Fresh bolts ensure full clamp load, proper damper function, and long‑term engine protection.

Specifications

• Part Number: 123680750
• Brand: Cummins Genuine OEM Part
• Fastener Type: Hexagon Flange Head Cap Screw
• Engine Compatibility:  ISX | QSX | 15L
• Approximate Weight: 0.21 lb

Why Choose Genuine Cummins Hardware?

Using genuine Cummins fasteners ensures proper fit, correct clamping force, and long-term reliability. Non-OEM hardware may not meet Cummins engineering standards and can lead to improper torque retention, premature wear, or component failure. The 3680750 cap screw is designed to perform as part of the complete Cummins engine system.

Installation & Service Notes

• Sold as a complete set of 12 Cap Screws. 
• Torque specifications vary by application
• Refer to Cummins service documentation for proper installation

NOTE: If you have any questions regarding the application or purchase of this bolt kit please Contact Us prior to making a purchase. We at KLM Performance want to ensure you obtain the correct replacement mounting hardware prior to installation of your crankshaft damper! 

• Engine: Cummins ISX 15L | Cummins QSX 15L | Cummins X15 
• Item Number: Cummins-ISX-QSX-X15-Crankshaft-Damper-Bolt-Kit
• Make: Cummins
• Model: Diesel
• Year :  2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025
• Manufacturer Part No: 
• Product Application: Early Cummins ISX, Cummins X15, ISX15, ISX12, ISX12G, ISX, and Signature 600 Engine Series produced from 2001 to 2025.
• Height : 3
• Width: 17
• Brand: Vibratech
• FAQ: What happens if I choose not to change the damper on my 2001 to 2025 Cummins ISX, ISX15, and X15 Engine? If you choose not to replace your Viscous Crankshaft Damper, the destructive torsional vibrations may lead to a cracked or broken crankshaft, valve train problems, and premature bearing wear.
• Part Number: Cummins-ISX-QSX-X15-Crankshaft-Damper-Bolt-Kit
• Manufacturer: Cummins
• Product Note: The Torsional Vibration Damper on your Cummins ISX, QSX or X15 engine is a wear item that requires replacement at the 500,000-mile mark.  The installation of a new Damper is strongly recommended in an effort to eliminate harmful torsional crankshaft vibration and ensure trouble-free operation. The replacement of the engine crankshaft damper is often overlooked during the In-Frame overhaul process due to costs. We at KLM Performance come across two different types of customers: the ones who choose to purchase a replacement viscous crankshaft damper and the ones who wish they had. The second customer is the one now dealing with a damaged crankshaft and other serious engine failures.