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Six-wheeler conversions: The truth about 6x4 and 6x6 ute conversions

Under heavy loads, six-wheelers can provide improved directional stability and handling. (image credit: Six-Wheeler Conversions Pty Ltd)

One-tonne 4x4 utes are well suited to the hard-working roles many tradies need them to perform - and that often requires carrying and/or towing heavy loads. However, utes can be easily overloaded without their owners being aware. Exceeding your ute’s GVM (Gross Vehicle Mass) or GCM (Gross Combination Mass) is dangerous, illegal and must be avoided.

There are two ways to address this common problem, depending on the size of the loads you need to carry. For example, if you’ve determined (after using a public weighbridge) that your overloading issue could be cured if your ute’s GVM was increased by up to half a tonne (500kg), then a GVM upgrade by a reputable and government-certified installer is often a convenient and effective solution.

However, if you need a GVM that’s considerably higher and you want to increase GCM, load length and off-road capability while you’re at it, then converting your ute from a four-wheeler to a six-wheeler could be the answer. If you’re interested in exploring this option, here’s a few things to consider.

Lifting weights

The increase in chassis length required to fit a third axle is usually 1000mm or more. (imag credit: Six-Wheeler Conversions Pty Ltd) The increase in chassis length required to fit a third axle is usually 1000mm or more. (imag credit: Six-Wheeler Conversions Pty Ltd)

A typical 4x4 tradie’s ute offers up to 1000kg of payload capacity, a braked tow rating of up to 3500kg, a GCM (or how much it can legally carry and tow at the same time) of around 6000kg and  can be driven with a standard driver’s licence.

Now, imagine its capabilities if it had up to 2000kg of payload capacity (or double the payload), an increase in braked tow rating up to 4500kg (or one tonne more) and a GCM increase which allowed it to legally haul those loads at the same time - still using a standard driver’s licence.

These stark weight comparisons showcase the potential of a six-wheeler ute in solving your overloading issues. And there are numerous other advantages.

The increase in chassis length required to fit a third axle is usually 1000mm or more, which results in a corresponding increase in tray length and therefore load space. Typically, a dual cab tray on a six-wheeler can stretch to around 2.6 metres, which can easily take two standard Aussie pallets, up to around 3.0 metres for an extra cab and around 3.6 metres for a single cab, which is almost long enough to land a light plane.

Under heavy loads, six-wheelers can also provide improved directional stability and handling on all road surfaces. In fact, a six-wheeler ute will typically carry a two-tonne payload easier than it would as a four-wheeler carrying one-tonne, due to better load distribution on a longer chassis and none of the tail-down-nose-up attitude often seen in conventional utes under heavy loads.

Other benefits can include reduced body roll when cornering, minimal pitch when accelerating or braking and negligible fuel consumption penalties, as sharing a heavier load across four rear tyres can also reduce rolling resistance due to less tyre sidewall distortion.

The 50 per cent increase in rubber contacting the road not only improves overall grip levels but, when combined with the third axle’s extra pair of brakes, provides a 50 per cent increase in braking capacity. Needless to say, the enhanced stability, grip and braking provided by dual rear axles can also greatly enhance a ute’s towing ability.

6x4 or 6x6?

A 6x6’s twin-driven rear axles are mechanically more complex than a 6x4. (image credit: Six-Wheeler Conversions Pty Ltd) A 6x6’s twin-driven rear axles are mechanically more complex than a 6x4. (image credit: Six-Wheeler Conversions Pty Ltd)

Depending on your six-wheeler ute’s working requirements, you also need to decide if you need the third axle to serve purely as a weight-bearing ‘lazy’ axle (6x4), or if it needs to deliver drive to its wheels (6x6).

A 6x4 lazy axle conversion typically retains the ute’s original rear axle/differential assembly with the new axle mounted behind it. A quality-engineered conversion can ensure excellent articulation between these two axles over large obstacles and that the majority of the load remains on the drive axle to optimise traction. The extra pair of rear tyres also increases flotation when driving over soft sand. Needless to say, under heavy loads a well-designed 6x4 can be a formidable performer both on and off-road.

By comparison, a 6x6 conversion delivers a whopping 50 per cent drive increase, which is why the military often specifies 6x6 drivetrains given the extreme off-road demands of battlefield service. A similar set-up could be just as beneficial for a heavily-loaded work vehicle particularly if it regularly encounters difficult terrain, like a mobile drilling rig for example.

However, a 6x6’s twin-driven rear axles are mechanically more complex than a 6x4 with more moving parts and potentially increased tare weights, which might reduce the load ratings available for standard licence holders. Even so, a quality-engineered 6x6 conversion can turn a humble 4x4 ute into an unstoppable heavy-duty workhorse.

Weights and measures

Not all six-wheelers can carry a 4495kg GVM while towing 4495kg at the same time. (image credit: Six-Wheeler Conversions Pty Ltd) Not all six-wheelers can carry a 4495kg GVM while towing 4495kg at the same time. (image credit: Six-Wheeler Conversions Pty Ltd)

As this article is a general overview, we won’t dig too deep into the numbers. The key ones to remember, though, are that six-wheeler conversions generally aim for a minimum GVM rating of 4495kg, which is as heavy as you can go using a standard driver’s licence.  

Braked tow ratings can also reach 4495kg (the maximum allowed for trailers with electric brakes), but that doesn’t mean that all six-wheelers can carry a 4495kg GVM while towing 4495kg at the same time. A few models can, but the GCM (Gross Combination Mass) is usually lower than these two figures combined.

Even so, they still represent huge increases in payload and braked tow ratings over the standard four-wheel utes they’re derived from. These conversions can also offer much higher weight ratings but require an LR (Light Rigid) truck driver’s licence to operate them.

Compliance

Buying a new ute and getting a six-wheeler conversion before its first road registration, the converter will fit a new compliance plate. (image credit: Six-Wheeler Conversions Pty Ltd) Buying a new ute and getting a six-wheeler conversion before its first road registration, the converter will fit a new compliance plate. (image credit: Six-Wheeler Conversions Pty Ltd)

There are numerous six-wheeler conversions available. Reputable companies have invested heavily in engineering, testing and government certification, so don’t waste your time and money - nor risk your safety - with a backyard operator that can’t provide the same. Needless to say, it’s not a simple DIY project either.

If you’re buying a new ute and getting a six-wheeler conversion before its first road registration, the converter (if approved by the Commonwealth Department of Infrastructure and Regional Development) will fit a new compliance plate. This certifies that it was first registered as a six-wheeler and for the life of the vehicle (unless modified again) it can be legally driven in all states and territories of Australia.

Quality converters might also fit other plates, stating the vehicle’s weight and towing capacities and, in some cases, recommended tyre rotation and pressure charts.

For vehicles that are already road registered before conversion, the approval process becomes a state/territory responsibility with protocols that vary according to the different road transport authorities. A freshly converted six-wheeler may have to be inspected by an authorised automotive engineer before being issued with a compliance certificate.

However, if the vehicle is later sold interstate, it may need to be inspected again by an authorised automotive engineer before being granted road registration in another state or territory. A reputable six-wheeler converter will be able to advise on all legal requirements for new and used vehicle conversions.

Do your homework

A quality six-wheeler conversion might just be the answer to all of a tradie’s overloading problems. (image credit: Six-Wheeler Conversions Pty Ltd) A quality six-wheeler conversion might just be the answer to all of a tradie’s overloading problems. (image credit: Six-Wheeler Conversions Pty Ltd)

The decision to convert your 4x4 ute into a 6x4 or 6x6 is not one to be taken lightly and justifies considerable homework to ensure you get exactly what you want in terms of six-wheeler conversions costs, quality of workmanship, government compliance and above all, performance.

So, shop around to see what’s available and don’t be afraid to ask lots of questions - quality conversion specialists will be more than happy to answer them. And also confirm if they back their workmanship with nationwide warranties and after-sales support. Some might even have ex-demonstrator six-wheeler utes for sale that could avoid the need to do your own conversion.

In any case, a quality six-wheeler conversion might just be the answer to all of a tradie’s overloading problems – and ensure ownership of one of the wildest-looking utes on the worksite!

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