JMACX Super Duty 300mm Chassis Extension Kit (Fitted)

The JMACX 300mm Super Duty Chassis Extension creates a more practical load-carrying setup for work, towing and touring. By placing the rear axle further beneath the payload, it helps improve support, balance and load distribution while adding more usable tray and canopy space.

The end result will look like a seamless integration. To achieve this we use highly skilled technicians to modify the chassis according to ADR (VSB14 requirements for post rego vehicles) rules. Our modification processes exceed the required vehicle laws. During this process all welds and modifications are rust treated, sealed internally and externally using an industrial chassis paint blend*.

Inclusions:

• Engineering certification that meets all States & Territories
• Fitting at JMACX HQ or authorised JMACX facilities
• Engineered 300mm chassis join section
• Super Duty one-piece tail shaft
• Extended brake lines
• Exhaust extension
• Fuel line extension

*As this is only applied to the modified area we would recommend you have the entire car rust treated to ensure comprehensive protection against future environmental exposure.

Why 300mm?

A 300mm extension provides the ideal balance between additional tray space and everyday driveability. It gives you more usable room for trays, canopies and equipment, while still maintaining a practical wheelbase and a well-mannered turning circle.

What’s the JMACX Difference?

JMACX uses a multi-layered structural methodology to provide a high-strength, dual-strength chassis extension while safeguarding the integrity of the original chassis. Our processes are unique in the industry and designed to deliver strength, consistency and long-term durability under demanding load conditions.

Pre Rego

For brand-new vehicles that have not yet been registered, the chassis extension can be completed before first registration. This allows the vehicle to leave fully engineered, approved and ready, with the compliant chassis extension already included in the build.

Post Rego

For vehicles that are already registered, the chassis extension is engineered to meet post-registration requirements, including VSB14 guidelines. The vehicle is certified after modification, with engineering documentation available for the signing engineer where required.

ADR Compliant

Engineered and independently validated to ensure compliant load distribution, structural integrity and safe vehicle operation under load. The system is approved for engineered registration Australia-wide, giving you confidence across all States and Territories.

OEM-Level Integration

Engineered to retain factory vehicle dynamics, driveline alignment, suspension geometry and chassis strength. The final result is designed to look and perform like a seamless integration, rather than an aftermarket add-on.

Heavy-Duty Construction

Manufactured using laser-cut 350MPa high-tensile steel, CNC forming and precision jig welding for strength and consistency. This delivers structural performance suited to heavy-duty work, touring, towing and off-road vehicle setups.

Driveline & Brake Extensions

The factory tail shaft is replaced with a purpose-built Super Duty one-piece tail shaft for maximum strength and reliability. The package also includes extended brake lines, exhaust extension and fuel line extension for a complete chassis integration.

Tray Options

In partnership with BOSS Aluminium, a range of premium tray solutions can be integrated into your chassis extension build. This gives you the option to pair the extension with a tray setup designed to suit your work, touring, towing or off-road requirements.

What If I Already Have a Tray?

If your vehicle already has a tray fitted, JMACX vehicle specialists can remove and re-install it at an additional cost. Some trays and canopies may require extra modification depending on the mounting system, fitment style and how easily they can be adjusted to suit the extended chassis.