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wheelbase modifications

Chassis extensions and modifications based on manufacturer instructions.


We can perform a range of modifications, including chassis extensions on any truck, according to original manufacturer instructions.

Wheelbase Modifications

At AA Diesel Truck Bodies, we perform all kinds of wheelbase modifications including both chassis extensions and shortening to suit your desired truck body specifications.

Engineer Certified

We do everything ourselves in-house from start to finish, using our very own expert qualified engineer, and all under one VASS certificate.

Manufacturer Approved

Our engineering team complete all wheelbase modifications by following exact manufacturer instructions to ensure results of the highest standard.

Minimising hassle

All of our wheelbase modifications and truck body installations are completed in-house, streamlining the build process and helping you get back on the road faster.


Learn more about our wheelbase modification procss from initial consultation to truck body installation.

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Consultation, truck measurement and weight distribution calculations

When going through the wheelbase modification process, we first take the time to understand the types of work that the truck body will be used for. This includes consulting about the types of jobs you might be doing, the machines you may need to carry, the routes you travel, the size of the truck body you would like to fit and many other factors. Once we have an understanding of your unique requirements, we then take the time to measure your existing truck and determine your weight distribution calculations. This includes weight distribution when under different types of load, the weight on the front and back, and the overhang.

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Preparing the truck for modification and pressing the new chassis in-house

Every truck manufacturer has their own unique requirements for how a wheelbase modification needs to be performed on their fleet of trucks. Typically, this means we need to either cut the truck in half, or roll the drive axles back according to the manufacturer’s specific instructions. When this is completed, we then press each new chassis using our own state of the art machinery, which is all performed in-house. Each chassis is double skinned for additional strength and durability.


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Modifying the tail shaft and optimising the driveline for performance and durability

A wheelbase cannot simply be modified without also modifying the sub-components of the truck body. This means we typically have to extend the tail shaft (we work out the maximum length based on your desired truck body) or add additional tail shafts (up to 3 or 4 in total). During this process we meticulously check all of the driveline angles and double check that everything is balanced. It is absolutely critical to get this part of the process correct to ensure that the driveline will continue to last long into the future. If this stage is not performed correctly, it can lead to vibration, oscillation and shuddering when driving at speed, meaning the driveline will eventually fail.


everything made in house

Assembly, extending the electronics and pneumatic airlines and painting

Once the drive shafts are finalised, and everything is assembled, we go through the painstaking process of extending all of the required electronics and the pneumatic airlines. Like the tail shaft modification, this can be a delicate and highly intricate task, as each manufacturer has their own unique way of routing electronic components and airlines. We take the time to understand the manufacturer requirements and get this right first time. When finished, the new wheelbase modification is painted to exactly match the existing chassis colour.

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Engineer evaluation, checking and issuing a compliance certificate

At this stage, the modification is complete and ready to go through our stringent compliance testing. Our highly experienced in-house engineer is involved in every step of the process from start to finish, evaluating the wheelbase modification, performing all of the required tests and checks. If everything is correct and meets the required standards, the engineer issues a VASS certificate for compliance.

wheelbase modifications

Fitting your new truck body

When the engineer issues the VASS certificate, your truck is now ready to have your new truck body fitted. Our wheelbase modifications are usually designed based on the truck body you choose. Typically, this involves a flat tray, beavertail tray, or tipper body. However, wheelbase modifications can be performed to ensure you can fit almost any truck body of your choice, and we regularly also build and fabricate custom bodies including cranes and crane sub-frames.


Truck body installation


Check out some of our latest wheelbase modifications by clicking on the articles below.

Isuzu F-Series Custom Beavertail Tray
Truck Trays

Custom Beavertail Tray For Isuzu Truck

March was another month of warm weather in Melbourne and another busy month inside the AA Diesel factory, designing and building a number of amazing truck bodies including this custom beavertail tray! Isuzu F-Series trucks are one of the most popular lines that we see regularly at AA Diesel, with our team having strong experience

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Kenworth Truck With Custom Body Parked In Workshop
Custom Truck Builds

Kenworth T610 Prime Mover With A 4.5M Custom Body

September has been a busy month for us here at AA Diesel Truck Bodies with a series of new and exciting projects. With the summer months just around the corner, we have been working closely with our clients across Australia to design, build and fabricate premium quality truck bodies, trays, and trailers. This month we

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Kenworth truck with tipping tray truck body
Wheelbase Modifications

KW Prime Mover Conversion with Chassis Stretch and 5M Tipper Body

In March we designed, built, and fabricated a range of prime mover conversions, tipper trucks, beavertail trays, trailer combinations, and chassis extensions. To wrap up one of our busiest months, one of our favourite jobs was a Kenworth prime mover conversion, which involved a chassis stretch to fit a custom 5 metre tipper body.

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Browse photos of our wheelbase modifications, extensions, and specialised jobs.

Get a free quote

Get in touch with us today to get a free quote for your wheelbase and truck body project.
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