How to pick the right 4WD for Outback travel

If you are planning to see more of Australia than places the highways can deliver you to, you will probably need a 4WD.

We say ‘probably’, because while you might get a modern two-wheel drive car or all-wheel drive SUV into many Outback spots, you might not be able to extract them.

You’re better off buying a 4x4 off-roader than risk getting stranded. Even a well-set-up four-wheel drive wagon or ute is not immune from getting stuck in the bush.

What 4WD you choose will, of course, be dictated by budget, personal preferences and practical requirements.

Practical requirements include whether the 4WD you want for Outback travel will actually work for driving in the city.

The biggest, toughest 4WDs don’t tend to be much fun doing three-point turns in narrow streets or fit too well in tight multi-level car parks.

Here we’re going through the important 4WD features and pros and cons of different types.

Many 4WDs are diesel-only, and for most buyers, diesel is a given anyway because the fuel is more readily available in remote country and diesels are usually more fuel efficient than petrols.

But deciding between a petrol or diesel 4WD to go bush is not the automatic ‘diesel or nothing’ choice it might first seem.

Thinking that a diesel engine is as simple as grandpa’s axe and will shrug off contaminated fuel with barely a hiccough no longer applies.

A modern, common-rail diesel is a highly-strung engine, and will not easily tolerate contaminated fuel or extended use for short city runs.

The modern high-pressure common-rail diesel engine will typically not cope well with dirty fuel. If such a diesel takes a drink of bad fuel, it’ll probably end up with more than a night at the mechanics getting its fuel tank pumped out.

The high-pressure fuel pump is easily damaged and may need rebuilding or replacing at a cost of thousands of dollars.

In a bad case of contaminated diesel entering a common-rail engine, the engine internals might require rebuilding or replacing. The bill for such a repair can easily stretch into five figures.

Buying diesel at larger, more popular fuel stations helps, as does adding an additional inline fuel filter and water separator.

Diesels running a diesel particulate filter (DPF) cannot be used for months on end of short urban hops either; they need a regular highway run to allow the DPF to burn off.

Otherwise the DPF can get clogged, and require an expensive visit to the mechanic to be pulled out and cleaned.

So a petrol 4WD might not be such a poor idea for Aussie Outback touring after all.

The main advantages of a petrol 4WD can include a much cheaper purchase price over a diesel and it can end up not using much more fuel in some touring situations.

Most petrol engines are relatively simple compared to a modern diesel. They might be a lot thirstier for short urban hops but they’ll do it without blocking the exhaust and they are less likely to go bang with bad fuel.

If you’re not going Outback to the extent you’ll need fuel drops for your expedition, then a petrol 4x4 can make more sense than a diesel.

It’s worth doing the research to see if a petrol might work for your situation.

A separate-chassis vehicle is one that has a body mounted onto strong longitudinal beams that are effectively the backbone of the vehicle.

A monocoque frame uses the stamped sheet metal floor and body all welded together as the structure to provide its strength.

There are fewer negatives for either design type these days. High-strength steels and aluminium have been used to good effect on both designs, making them both rigid and strong.

A ‘hybrid’ type of monocoque/chassis with chassis beams and a strong body are also more commonplace.

A separate-chassis design is all you’ll get when buying a one-tonne ute. The ute’s open tub or tray does not exactly serve as a good structural support, if it were a monocoque design.

The ute’s high payload requirement also makes a separate chassis a no-brainer.

As for 4x4 wagons, while chassis rails used to offer better protection for underbody components against off-road damage, a well-designed monocoque underbody can be just as strong and protected, although in practice it’s not much lighter.

In theory, a separate-chassis vehicle will sit taller on the road because it has its body sitting on the chassis. This can have implications for multi-level car parks (maximum height clearance) and centre of gravity issues (more prone to roll-overs).

Live axles are typically tougher and stronger than independent suspension, and usually have better axle weight ratings and therefore bigger payloads.

They can offer excellent wheel articulation (more so with coil springs than leaves), which keeps wheels on the ground more and so provide better grip and stability than an independent suspension.

Live-axle suspensions tend to not chew out bushes as easily as a heavy 4WD sitting on independent suspension.

The problem is that a live-axle 4WD’s ride quality over rough terrain is usually terrible, when compared to a good independent set-up.

Also, independent suspensions today have improved wheel travel compared to the woeful examples available in the 1990s.

Electronic traction control and factory diff locks has meant new 4WDs slip less than ever off-road, even if they are not quite as stable when having an independently sprung wheel or two hanging in the air on an undulating track.

You will need a 4WD with some kind of low-speed gearing to be effective off-road.

While there are exceptions, such as the Volkswagen Amarok which has a single-range transmission with a crawler first gear, the most popular type is a dual-range transmission or transfer case.

A dual-range transmission has two sets of gear ratios available, one normal set for road driving and another, lower set for slow trail driving.

Low-range gearing multiplies the torque from the engine and also limits the speed that the vehicle can achieve.

You’ll need both to successfully traverse many Outback tracks.

There are so many varieties of four-wheel drive systems we’ve written a separate article to describe them all. Here we’ll attempt to give you a basic run-down with pros and cons.

There are two basic types of 4WD: part-time and full-time.

Part-time 4WD runs 2WD only until 4WD is manually selected by the driver, which fixes drive from the transfer case at a 50:50 split to front and rear axles.

You can only actually use 4WD for part of the time – that is, for when the surface is slippery, such as on dirt, mud, ice and snow.

On firm, grippy surfaces like paved roads, you must select 2WD only. There is no ‘give’ at the transfer case with the 4WD torque split, so if part-time 4WD is used for any length of time on surfaces where there is no slip (such as a dry paved road), damage can occur to the transfer case.

It’s a simple system, and can be slightly more fuel-efficient, but you need to remember to activate/deactivate as road surfaces change. Most utes on the market, like the Ford Ranger and Toyota HiLux have part-time 4WD.

Full-time 4WD runs, as the name suggests, in 4WD all the time. But a full-time 4WD will need the centre diff lock activated when in high range (which locks drive 50:50 between the axles, like a part-time 4WD) when things get really slippery.

Otherwise drive will potentially go to the wheel with least traction, and depending on how clever the traction control is, it may spin uselessly.

Like a part-time 4WD, a full-time 4WD running with the centre diff locked on dry surfaces will cause damage. The Toyota LandCruiser Prado and LandCruiser 300 Series are examples of vehicles with full-time 4WD.

Low-range works much the same in both part- and full-time 4WD systems. With some (full-time 4WD) exceptions, drive is locked at 50:50 front/rear and so you have to use low-range only where the surface allows some wheel slip.

The Mitsubishi 4WD system, such as fitted to Triton, is effectively a combination of both part-time and full-time 4WD, offering high-range 2WD, full-time 4WD and 4WD centre diff locked 4WD (and low-range locked, of course).

On-demand 4WD (also called torque on demand) is a hybrid of part-time and full-time 4WD when used in high-range, at the least.

This system is set-and-forget like full-time, but it operates in its standard setting like part-time. So it will run in 2WD only until the vehicle detects wheel slip, when the system will engage four-wheel drive. The Ford Everest is an example of a vehicle with on-demand 4WD.

All 4WDs have some type of individual wheel traction control now, with electronic traction control (ETC) and/or mechanical differential locks.

In most cases, this has allowed standard 4WDs to get much further on slippery off-road tracks than they ever have without losing traction.

The better types will allow front ETC to operate with the rear diff lock engaged (or, in rare cases, such as the Jeep Wrangler Rubicon, have both front and rear diff locks as standard).