Product Introduction

This is a standard, single-turn spring washer designed to provide continuous tension in bolted joints, preventing fasteners from working loose under vibration.

• Structure & Material: Made from high-carbon spring steel, it features a single, split coil design. The surface is coated with a black oxide finish for corrosion resistance.

• Performance: When compressed, the washer exerts a constant spring force that maintains tension in the joint, counteracting the tendency of nuts and bolts to loosen due to engine or road vibration.

• Durability: The high-carbon steel construction resists fatigue and maintains its spring tension over long periods, ensuring reliable performance in harsh operating conditions.

• Compatibility: A standard metric component (M6 thread size) that fits a wide range of applications in the vehicle’s chassis, engine, and transmission systems.

Core Function

1. Anti-Loosening: Prevents nuts and bolts from loosening under vibration, which is critical for maintaining the integrity of critical vehicle systems.

2. Tension Maintenance: Maintains a constant clamp load in bolted joints, preventing leaks in sealed connections and ensuring proper alignment of components.

3. Compensation: Compensates for minor settling or relaxation in the joint over time, ensuring consistent performance.

Spring Washer Q40306 – SINOTRUK HW Series Gearbox | OEM Quality, Factory Direct

When it comes to keeping your SINOTRUK HW series gearbox running smoothly, every small component matters — and the Spring Washer Q40306 is no exception. This precision-engineered elastic washer plays a critical role in preventing bolt loosening caused by heavy vibrations, thermal cycling, and constant torque loads inside the transmission housing. Designed to meet OEM specifications for SINOTRUK HOWO heavy-duty trucks, this spring washer ensures reliable fastener retention across thousands of operating hours.

At Mettlead, we supply genuine-quality Spring Washer Q40306 for SINOTRUK HW series gearbox applications directly from our manufacturing base in China. Whether you are a wholesale distributor, fleet maintenance provider, or regional parts agent, you will benefit from factory-direct pricing, bulk availability, and consistent product quality backed by strict inspection protocols.

Key Features and Benefits of Spring Washer Q40306

So, what makes this particular spring washer indispensable for HW gearbox assemblies? Let’s break it down:

• Anti-Loosening Performance – The split-ring design generates a continuous spring force that resists rotational loosening, which is especially important in high-vibration gearbox environments.
• OEM-Grade Material – Manufactured from hardened spring steel with surface treatment to resist corrosion and fatigue, matching SINOTRUK original equipment standards.
• Precise Dimensional Accuracy – Produced to tight tolerances ensuring proper fit within the HW series gearbox bolt assemblies without interference.
• High Fatigue Resistance – Engineered to withstand repeated compression-recovery cycles without permanent deformation, even under sustained thermal loads inside the transmission.
• Cost-Effective Bulk Supply – As a factory-direct supplier, Mettlead offers competitive wholesale pricing that protects your profit margins on high-volume orders.

In other words, this spring washer is not just a commodity fastener — it is a precision component that directly contributes to gearbox reliability and reduced maintenance downtime.

Application Scenarios: Where Does Spring Washer Q40306 Fit?

The Spring Washer Q40306 is specifically designed for use within SINOTRUK HW series gearboxes, which are widely installed across HOWO heavy-duty truck platforms. More specifically, you will find this component in the following applications:

• SINOTRUK HOWO A7 / T7H / T5G trucks equipped with HW19710, HW19712, and HW15710 transmission models
• SITRAK C7H series with HW gearbox configurations
• Gearbox housing and cover assemblies – securing bolts that hold bearing caps, shift covers, and side plates
• Internal gear train fastening points – wherever anti-vibration bolt retention is required inside the transmission

Because the HW series gearbox is one of the most widely deployed heavy-duty transmissions across Africa, Southeast Asia, the Middle East, and Central Asia, demand for this spring washer remains consistently high among regional parts distributors.

Looking for more SINOTRUK gearbox components? Browse our full range of SINOTRUK HOWO gearbox parts or explore our complete gearbox parts category for related items.

Technical Specifications

Below you will find the detailed parameters for the Spring Washer Q40306 SINOTRUK HW Series Gearbox. These specifications reflect OEM-equivalent standards:

OEM/ODM Capability and Custom Packaging

As a professional supplier of Chinese brand truck parts, Mettlead understands that different markets have different branding requirements. That is exactly why we offer flexible OEM and ODM services for the Spring Washer Q40306 and other gearbox fasteners:

• White-Label Packaging – We can ship with neutral packaging, allowing you to apply your own brand labels for seamless integration into your product line.
• Custom Packaging – Need branded boxes, specific labeling formats, or barcoded packaging for your warehouse system? We accommodate custom requirements at scale.
• Strict Quality Control – Every batch undergoes dimensional inspection, hardness testing, and surface quality checks before shipment. Consequently, you receive consistent product quality order after order.
• Bulk Order Flexibility – Whether you need 10,000 pieces or 500,000 pieces, our production capacity supports your stocking demands with short lead times.

Furthermore, we welcome international buyers to visit our facilities in China for on-site inspection and quality verification. This transparency builds the trust that long-term partnerships require.

Explore our full catalog of SINOTRUK HOWO truck parts to discover additional components for your inventory.

Customer Case Study: Spring Washer Q40306 Bulk Supply to East Africa

To illustrate how our supply chain works in practice, here is a recent example involving the Spring Washer Q40306 for SINOTRUK HW series gearbox applications:

In early 2024, a truck parts distributor based in Tanzania reached out to Mettlead. They were sourcing SINOTRUK HW gearbox spring washers along with other transmission fasteners for their growing aftermarket business. Their primary challenges included inconsistent quality from local suppliers, long lead times, and lack of proper packaging for retail resale.

After receiving samples of our Spring Washer Q40306, the client confirmed that dimensional accuracy and hardness met their requirements. We then fulfilled an initial order of 50,000 pieces with custom-branded packaging designed for their distribution network. Delivery was completed within 18 days via sea freight to Dar es Salaam port.

Since then, this client has placed three repeat orders and expanded their purchasing scope to include additional SINOTRUK HW gearbox parts such as snap rings, seals, and bearing assemblies. The relationship demonstrates how factory-direct sourcing from Mettlead delivers both margin advantage and supply reliability.

Frequently Asked Questions (FAQ)

What is the function of Spring Washer Q40306 in a SINOTRUK HW gearbox?

The Spring Washer Q40306 acts as a lock washer that prevents bolts from loosening due to vibration and thermal expansion inside the HW series gearbox. Its spring tension maintains clamping force on the fastener, which helps protect internal transmission components from damage caused by loose connections.

Is this spring washer compatible with all HW series gearbox models?

Yes, the Q40306 spring washer is a standard fastener used across multiple HW gearbox variants, including HW19710, HW19712, HW15710, and related configurations found in SINOTRUK HOWO and SITRAK trucks. However, we always recommend verifying against your specific gearbox assembly drawing or parts catalog.

What material is the Spring Washer Q40306 made from?

This spring washer is manufactured from 65Mn spring steel, which is then hardened and tempered to achieve an HRC hardness of 44–51. Additionally, it receives zinc plating or phosphate treatment for corrosion resistance. These material properties ensure long-term elasticity and fatigue resistance under gearbox operating conditions.

Can I order Spring Washer Q40306 with my own brand packaging?

Absolutely. Mettlead offers both white-label and fully customized packaging options. You can supply your brand artwork, and we will produce packaging that matches your market requirements. This service is available for bulk orders at no significant additional cost.

How does this spring washer differ from a flat washer?

Unlike a flat washer, which simply distributes load, the Spring Washer Q40306 has a split-ring design that creates axial spring force. This force actively resists rotational loosening of the bolt. In a gearbox environment where constant vibration is present, a spring washer is essential — a flat washer alone would not prevent bolt backout over time.

What is the minimum order quantity for wholesale buyers?

Since the Spring Washer Q40306 is a small fastener, we typically recommend ordering in bulk quantities to optimize shipping costs. Specific MOQ depends on your total order composition. Contact us directly with your volume requirements for a tailored quotation.

Ready to Source Spring Washer Q40306 at Factory-Direct Pricing?

If you are looking to secure a reliable, cost-effective supply of Spring Washer Q40306 for SINOTRUK HW series gearbox applications, Mettlead is your direct channel to the source. We offer competitive wholesale pricing, consistent OEM-grade quality, flexible packaging, and fast logistics support to markets worldwide.

Take the next step today:

• Request a quotation with your target quantity and destination
• Ask for free samples to verify quality before committing to bulk orders
• Discuss custom packaging or white-label options for your market

Contact us now to get your personalized quote and start building a profitable supply partnership with Mettlead.