Building a Legal 4WD in 2022

Honestly, building a legal 4WD is tough when all the marketing and hype I’m exposed to highlights illegal modifications, but doesn’t say that in any fine print (paper or online). Learning the relevant laws in relation to each modification I want to do has been eye opening.

If you watch YouTube, as I love to do, you may think that so many doing a similar thing must be right. Right? Wrong! Many of these influencers, or whatever they’re called, are making content for popularity and money whilst providing misleading information with illegal modifications.

I picked up my new Dmax X-Terrain in July 2021. I had been researching the build for about two years. When I began to contemplate my first modification and started reading the rules, I realised just how bad Youtubers are with their vehicle builds. Not all, but it seemed most of them are purporting illegal modification information.

The worst part, is that if you watch Youtube, they make you believe you need all these silly modifications in order to tour Australia or explore the Victorian High Country (VHC). The truth is very different from what these people output for views and money.

A Little Fact

You can drive 80% of the Victorian High Country with nothing more than a stock 4wd (low range and rear diff lock) with all terrain tyres and a snorkel. That’s it! Two modifications to drive the majority of the steepest, harshest, 4WD’ing country within Australia. Hell, the snorkel you can get factory fitted on most 4×4’s today.

The other 20% is what gets shown on Youtube, the tougher terrain, and the build modifications needed to drive that. The problem is that most of these Youtubers don’t drive that other 20% at all. They purport a need for thousands in modifications to drive the 80% off-road that can be done with just two modifications.

Do You Need The Modification?

Have you tried getting where you want to go without the modification? Modern 4WD’s are extremely capable, why not give it a try before you make unnecessary changes.

Track classification is a quick indicator for what modification level you actually require:

  1. Easy – An all wheel drive vehicle with highway or all terrain tyres.
  2. Medium – A 4WD that has low range, rear diff lock, snorkel and highway or all terrain tyres.
  3. Difficult – Medium plus legal lifted tyres, suspension, winch, mud terrains may apply here.
  4. Very Difficult – Engineered purpose built vehicle (big tyres, suspension, power, etc).

The Youtube problem is that people build a vehicle for the very difficult, but don’t get it engineered so its legal and insurable. Not just for them, but if they hit you. Worse they carry-on like that is what you need to drive simple off-road tracks, to drive on the beach or such simple things.

To drive around Australia with your caravan, that falls into the Easy category. That includes parking on beaches and driving the tracks into popular tourist attractions and the iconic roads / tracks. Changing your tyres, size for size, to all terrain for puncture resistance is the key modification. That’s it. You can do all the popular tourist tracks with just a tyre change.

Our Requirements: We want a legal build that in the event of any accident, our insurer has zero reason to disqualify payout, for us or anyone else involved. We want to travel the Victorian forestry and off-road areas, but holiday in locations all over Australia. We want to drive difficult tracks and below in rating. Difficult tracks can be safely driven with traction, lockers, better clearance, approach / departure angles and winch / recovery gear.


I wanted to quickly mention weight, as everything you do to your 4WD affects it. Weight is a legal requirement that is being enforced more than ever before. 4WD’s and caravans are being pulled over and weighed for GVM & GCM compliance. Overloaded 4WD’s towing are losing control and killing people. The problem has become widespread with law enforcement Australia wide aware and trying to fix the problem.

The Weight Solution – GVM Upgrade

GVM upgrades are a blessing and a curse. The blessing is that you can add more weight. The curse is that the engineering associated to GVM upgrades does not include upgraded brakes to help stop the extra weight, larger axles, diff housing strengthening, and so on. Suddenly you find yourself in the middle of nowhere with a broken axle or bent chassis due to a heavily corrugated road.

The Real Weight Solution

The best thing you can do is cut back your modifications and equipment. That simple. The next best thing you can do, is pay for the lightest, strongest accessories and equipment, not the cheapest, heaviest. They cause the problems. You can absolutely cut 10kg, 20 times in buying accessories and making choices. You will not however cut 200kg from a single choice. Buy hiking products which are lighter than camping products.

People choose to camp and explore for a simpler time, yet they complicate the crap out it by wanting to bring the kitchen sink. Being comfortable is a good nights sleep and comfortable chair. Everything else is possible bloat.

Axle Load

Every vehicle has an OEM axle load rating, eg. 2021 Dmax is 3360kg. The only way to change that rating is through engineered changes (strengthening, reinforcing, larger parts) and testing. GVM upgrades surpass the OEM axle rating without any of the engineered requirements, eg. 2021 Dmax OEM GVM 3100kg – GCM 5950kg, Lovells GVM upgrade 3600kg, GCM 6900kg with suspension only.

Here is the problem and why I’m raising this. If you’re getting a GVM upgrade for your work vehicle, driving on road from job site to job site, no problem more often than not. Well, braking is still an issue. When you take that GVM upgrade off-road, onto outback heavily corrugated roads, tracks, that is where loading beyond your axle rating causes problems, and usually quickly.

The outcome, bent chassis (just google that one for a good time), broken axles, broken diff housings, and driveline damage. You know? The important parts you need for your vehicle to move! If you need to surpass your vehicles axle load, and are taking your vehicle off-road, you’ve either, a. purchased the wrong vehicle, or, b. need to seriously cut your wants from the vehicle to shed weight.

If you need to surpass your OEM axle load, you’re starting with the wrong vehicle. That simple. Maybe look at an Iveco 4×4, as it will likely suit your needs from the factory without modification for around $110,000, no need to GVM or GCM upgrade that.


In Victoria it’s legal to lift your 4WD suspension 50mm (2 inches). With modern IFS vehicles its impracticable to lift them beyond that due to compromising the safety systems. Selling or buying a 3″ lift kit is legal, fitting it and driving it on the highway is illegal. Anything beyond 50mm at the front and rear axle requires testing certification. There are a lot of uninsured 4WD’s driving as a result of modifications.

Lifting a modern vehicle 2 inches is headache enough, requiring a diff drop to reduce CV angle, new adjustable upper control arms or ball joint relocators to correct castor from the lift, and then changing the vehicles center of gravity making your new pride and joy more susceptible to rollover. Oh, did I mention raising an IFS beyond 50mm usually reduces the articulation, the very thing you think you’re improving, but actually making worse. It will never drive better than it does OEM from the dealer. Think carefully before changing how your 4WD drives.

Ask yourself – do you really need a lift? Have you tried getting your 4WD where you want without a lift? That was my priority. Take your vehicle where you plan to use it, or similar settings. Not lifting your 4WD has more advantages than lifting it, drive, sway, handling at 100kph, to safety systems operating as intended from engineered distance to ground.

I was shocked how far my Dmax went off-road straight from the showroom floor, no changes. The highway tyres are impressive off-road in the wet and dry, but clay and rock is where they failed miserably making mountain travel unsafe. Expect that with highway tyres.

If you want to actually learn the pro’s and con’s to lifting an IFS, watch two videos.

Rims & Tyres

Wheel track, height and weight, are issues in selecting the right wheel combination. Changing OEM Highway Terrain to All Terrain adds approximately 5kg per tyre. It adds 7-10kg going Mud Terrain. Times that by 5 wheels. Go bigger and you add 15-25kg per wheel.

Who said bigger is better? Your mates, YouTube, local tyre store! For every change you make to your tyre and rim combination, you change the vehicle dynamics. That is a fact. Chances are you only need a good all terrain if travelling Australia. If you go looking for the tough stuff, that’s a different story. But general remote travel in Australia can be achieved on OEM size all terrains with no issues. Yes, I’ve travelled a lot of remote Australia.

Wider tyres give greater stability, but increase weight, increase turning circle, worsen fuel economy and add driveline wear. Taller tyres get you through ruts and over obstacles easier, but increase vehicle roll, affect emergency systems such as ESC, make your vehicle less stable, decrease power and torque, and increase fuel use.

The law allows for a total change in track width up to 50mm and 50mm tyre diameter (OD) (25mm maximum lift). Don’t rely on online generic tools, find your OEM exact match tyre OD and compare with the OD for the tyre you want to use. If its less than 50mm difference its ADR compliant. If not, even by 1mm, you have given an insurer a reason to reject your claim in the event of the worst. I’ve found that any change in rim offset by more than 13mm will likely make your total wheel wider than the legal limit (rim + tyre).

For a laugh, if you want to see what a stock vehicle with a set of all terrains can do, then watch WhistlinDiesel try and destroy a 1989 Toyota Hilux, dubbed the most indestructible vehicle in the world by Top Gear. Take note of the big wheels, big lift, purpose built vehicle he is with, and a stock hilux with AT’s does it all. Watch the whole series if you haven’t, he punishes this thing and it keeps starting.

My Story: I want that 25mm lift, and I was sitting here trying to excuse going over that 50mm OD increase by up-to a few millimetres. End of the day I reigned my thinking back. What does a few mil really matter? Not much. My OEM OD is 781mm. My new OD will be 825mm (275/65/18). 3mm loss of lift means nothing vs keeping it legal. If I went to a 285/65/18 the OD was 832mm. Just 1mm over, but still over. I wanted to step down to 17″ but that put me at 837mm OD. Again, just over. Still illegal. I’m sure I could find a brand that gave me the extra 3mm if I looked, but I want Maxxis based on their reviews.

Changing your rims and or tyres has significant consequences. Proceed cautiously.

Another example of bad Youtube exposure, adding 17×9 – 0 offset rims with 305/70/17 tyres in NSW. The legal allowable track increase is 50mm in NSW, this has increased the track by 104mm. Absolute stupidity from a 4×4 shop backing illegal modifications for Youtube views. They even discuss getting the grinder out to modify the chassis to stop the scrubbing. Another illegal modification. But hey, go the views and ad dollars.

Power Increase

Off Road and Passenger Vehicles manufactured on or after January 1986 and Commercial vehicles below 2.7 tonnes GVM manufactured on or after July 1988 must not have any modification that significantly increases engine performance or otherwise affects exhaust emissions unless certified by a VASS Signatory.

For everyone who has dyno tuned their 4wd, added a chip or other means of artificially inflating engine power, they are illegal modifications unless VASS certified.

This does not include throttle controllers, as they do not increase engine performance, they only manipulate where you can use the existing performance the engine already produces.

To be legal, you have to run this past an engineer for stamping. Who knew? I do now. With so much Youtube exposure, getting that extra power, you would think its legal. But nope.

DPF / EGR Modifications

It is illegal to remove your DPF or bypass EGR. You DO NOT get massive power gains removing either.

The DPF affects power by approximately 0.5kw. That’s it. That little. Watch below testing. You can add that back with a slightly larger exhaust, DPF back, all without making your car illegal, risking massive fines or jail time. EGR serves a legitimate environmental purpose. EGR removes NOx emissions, it’s not a tool for more power.

Roof Load – Weight & Height

Do you need a roofrack? Really? The majority of 4WD’s I see have a roof rack holding an awning or lightbar. Why? These vehicles often can’t fit within parking garages at local shops because of the roof rack accessories. Most won’t fit in their own garage. To me this represents a mighty expensive and inefficient outcome.

Maybe you have a legitimate reason for a roof rack, but do your homework with load ratings and understand what you’re buying (static, dynamic & off-road load ratings). Don’t overload your roof rack, making it illegal.

Your vehicle has a rated roof load. This rating cannot be exceeded. This rating includes the weight of the roof rack. This can often leave you with nothing more than 20kg – 30kg roof capacity off-road, maybe 50kg dynamic on sealed surfaces. Most racks I see with a lightbar, awning and maxtrax attached, are over-loaded. That fast, that simple.

A roof rack is often around $1000 – $1500. That’s an expensive investment for little weight storage. Bars may do the job just as well, cheaper and lighter, allowing better options.

I’m going to install a tub rack, not roof rack. A roof rack decreases fuel consumption and is difficult to access, a tub rack is tucked away with less resistance to wind, nice and low for ease of access. If you want a roof rack for load on a ute, then a tub rack is the best choice IMO. My tub rack limit using FrontRunner is 300kg. No downgrading.

Do your homework. Don’t follow the marketing nonsense.


Again Youtubers, not who they are as a person, but the idiotic modifications they do for views, which are totally illegal, but don’t say its an illegal mod. For example, just watch Ronny Dahl add eight spot lights to his Hilux.

Eight forward facing lights are illegal, even in WA (Ronnys home state). Read here for that evidence. States tend to comply with ADR for modifications nowadays, all states working from the same sheet of paper. Finally! Four (4) forward facing lights are the legal allowance. Lights in pairs must be symmetrical at the vehicle centre. All lights must be white in colour. Lightbars must be centred to the vehicle. All additional forward facing lights must be switched to only activate with high beam.

What is it with 4WD’ers wanting to see 1km down the road? You can’t clearly see 1km down the road in the day, let alone night with artificial lighting. You’re only looking for large obstacles at that distance. If you’re an 80+ tonne B double or triple, sure, makes sense based on how long it takes them to stop on a highway. A 4WD that weighs a few tonne and can safely pull-up in a hundred metres? Maybe a bit silly?

If you can’t achieve what you need from four extra lights, you’re doing it wrong. In all honesty, one set of good spots or floods on the front will do the job for you. One decent dual row lightbar can make night as day for a few hundred metres in front. Do you need more than that?

Then you have positioning of lights. You can’t just add them anywhere. Read the rules for your state.


Any type of spacer you add to your wheels is illegal. You can add body spacers to raise the body of the vehicle, but that must be VASS engineer signed off. Some states allow small body lifts without certification, but not Victoria. Remember, body lifts will add a gap around your vehicle (wheel arch protection, bumpers, etc).


Exhausts are pretty simple. You can’t end your exhaust earlier than where the manufacturer had it, you can’t remove catalytic converters, DPF or sensors and obviously it can’t exceed noise regulations. I’m not sure you would want to do crazy things with your exhaust, as it affects your vehicles power if you go too large or small. They really are a just right part with a little scope either side for movement.

A slightly larger exhaust is good for cooling. Lowering your EGT allows your engine to work a little harder without throttling engine power under harsh operating conditions (towing, remote or off-road, combination)

Additional Fuel Tanks

This is tricky. From my understanding reading the VSB documents, its legal to fit an approved long range tank (ARB, Brown Davis, certified replacement tanks) because the tank mimics all OEM fittings with zero modification. It is that part that puts this one thing into the legal column, zero modification, direct OEM replacement. Oh, and they’re below adjusting it beyond a fixed percentage.

It is legal to replace OEM parts for direct replacements, but it is illegal the moment you have to modify any part of the fuel system. So for anyone who fits an additional tank to their vehicle and modifies the fuel system to drain or pump from an additional tank to the OEM tank, that is illegal without certification from a VASS authority. As are 30% injectors and increased diesel pump without VASS certification.

It is legal to store portable fuel, ie. jerry cans, but even that comes with conditions. It can’t be located that it could cause fire on impact of front or rear collision. Pretty much, don’t mess with your fuel system beyond direct replacement part for part. Oh, and don’t put a fuel jerry on the back of your vehicle.

Bar Work

This isn’t super complicated, and really only applicable if you’re going out to get custom work done. Any tech you have installed must go back exactly where it was OEM and work as intended. Outside of that, you can get creative if you want to go custom.

Pretty much anything you buy from a large company, they’ve already done all the compliance and ADR certification, its just changing part for part and everything fits and works as OEM.

The biggest problem with protection is the weight. Back to that problem again. Your average ARB & TJM hooped bullbar weighs around 90kg. Go to someone like Offroad Animal and it drops to 60kg. Massive weight difference for a little extra cost. A TJM rear bar / tow for the new Dmax is $1400 and weighs 72kg. Offroad Animal rear bar / tow is $2150 and weighs 50kg.

Shopping around, paying a little extra, can save you significant cost in other areas such as not requiring a GVM upgrade, or allows you to add essential items you’ve deemed necessary without exceeding an upgraded GVM / axle rating.


Fairly common-sense this one. You can upgrade your existing brakes like for like without certification, though if you substitute disc for drum, then that entire system must be installed and VASS certified.

There are a lot of brake packages available, and those are legal to swap as a like for like, ie. changing OEM disc for a performance disc setup. If overall size changes (disc + caliper) back to VASS certification. Many aftermarket systems are pre-certified as direct replacement for each model, ie. Pedders or Bendix.

Beyond the obvious, brakes are an important upgrade if you’re adding accessories and making your vehicle heavier. One of the first things you will begin to notice is your vehicle becomes harder to stop. Well, it will take longer to stop, is the more important thing. Harder in an emergency because of the weight.

There are affordable methods to improve your braking. Changing out the rubber lines for braided is one way. The rubber expands under pressure when braking, where the braided line is tougher and holds true under pressure, thus less pressure is needed at the brake peddle to brake. Upgrading just the front discs to a performance one can make a significant improvement. You have to get brakes done eventually, so do them when due, just change them for a better version.

When my front brakes are due for replacement, I’ll change them to performance. The rear drum I will be changing out for disc when we buy our camper and start towing off-road. Honestly by then, the rear drum will probably be due for replacement, so I’m getting some value from OEM equipment first.

Cooling Systems

In Victoria its legal to change your intercooler or radiator for a performance one, being direct replacement parts. Whilst they may provide small performance increases, that is due to the extra cooling those systems provide, so your engine can work a little harder according to the electronics. They’re a legal way of minor power increase without VASS certification, but more importantly, they allow your engine to work harder in the tough stuff (tracks / ambient temp) and not put your vehicle into limp mode due to excessive heat.


I still watch lots of Youtube, but I honestly don’t listen to advice from these people. I watch them for entertainment value, but certainly not advice. There are some who give excellent advice and guidance, very legal advice and experience. If you were to believe 4WD247 you need $30k of mods just to tour Australia. Last month a Dometic fridge is best, this month a MyCoolman, suddenly a Kickass one is the one to buy. See the picture being painted? Who pays most they endorse, not the best product or service.

IMHO, I would love to see insurers reject claims based on vehicles not being roadworthy (illegal modifications). I think it needs to be done in order to get the group legal, or a whole lot more legal than it is right now. If many of these 4WD’s were to hit your vehicle, fully insured, it would be hit and miss whether their insurer would cover you. I remember watching one Youtuber talk about insurance, the insurer had them send pictures of the vehicle, and they sent back immediately rejecting to insure them based on the vehicle which was heavily, illegally modified.

I’m not saying that building capable off-roaders for very difficult tracks is a bad thing. It’s not. The problem is that people aren’t building compliant vehicles, then driving them at 100kph on the road with us all.

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