So, you’ve got yourself a 4WD. The real question is when do you use it? When do you get out and lock the hubs (if you have an older 4WD), or turn the dial from 2H to 4H, or 4L?
A 4WD has the benefit of extra clearance over a normal SUV or soft roader, but they also have the ability to send drive to all 4 wheels. However, 4WD should only be engaged under certain circumstances. If you do it under the wrong conditions you can have some pretty substantial problems.
Different 4WD setups
2H to 4H to 4L
The large majority of 4WD’s out there are rear wheel drive only, and driving around normally in town you’ll be in 2H (2WD). When you put it into 4WD high range (4H), or low range (4L), you get front wheel drive as well.
This is done by locking hubs on the front (manual or automatic) and shifting the lever, or dial across from 2H to 4H. Most do not have a diff lock in the centre, so the moment you put it into 4WD, the front and rear axles are locked together.
Some vehicles can do this on the fly (just 2H to 4H), and some require you to be stopped. Going from 4H to 4L generally requires you to be stopped, in neutral and it takes a couple of seconds.
On the bitumen you drive around in 2H. When you leave the bitumen, you’ll engage 4H, or 4L.
Some 4WD’s drive all 4 wheels all the time (on the bitumen too), and are known as constant 4WD. This includes many of the Toyota Land Cruisers. These operate similar to an all wheel drive vehicle until the centre diff lock is engaged. In essence, you are in 4H all the time, until you engage the centre diff lock.
When the centre diff button is engaged, you go from constant 4WD to locked 4WD, or what most people would traditionally know as 4H. From there, you can go from 4H to 4L, which uses a different set of gears but still keeps it in full 4WD.
On the bitumen, you’ll leave the vehicle in 4H but without the centre diff lock engaged. When you leave the bitumen you’ll hit the centre diff lock to engage true 4H, or stop and put it in 4L. Generally 4L forces the centre diff lock to come on anyway.
RWD/4WD with a centre diff lock
There are a couple of interesting products on the market to confuse people in regards to selecting 4WD. Mitsubishi for example have a product called Super Select, which allows you to drive around in 2WD, as well as 4WD without the centre diff lock engaged, and then 4H with the centre diff engaged, and then 4L.
This means that many of the Mitsubishi models can drive on the road in 4H, as long as you don’t have the centre diff lock engaged. 4H without the centre diff lock is exactly the same as a constant 4WD Land Cruiser. Mitsubishi actually recommends that you tow in 4H, as you have more traction. Just remember not to engage the centre diff lock unless you are off the bitumen!
4WD on bitumen
Unless you have a centre diff with the ability to lock it, you should not be driving on the bitumen in 4WD. 4WD is designed for terrains where slippage can occur, like sand, mud, gravel and rocks. This means for most 4WD’s, you are stuck in rear wheel drive only when on bitumen.
If you own a 4WD with a centre diff lock like a Land Cruiser 80 series, or 200 Series, or a Mitsubishi Pajero you are perfectly fine to drive around in 4H without the centre diff lock engaged, and Mitsubishi actually recommend this when towing.
When should you engage 4H?
In most circumstances the moment you go off the bitumen its a good idea to put the vehicle in 4WD. The only time that this is not encouraged is if you are going back onto bitumen in a very short distance, or if the road condition is extremely good and you don’t need the extra traction. There are some gravel roads that have been graded so well that they are smooth as and have minimal loose rocks on the top.
You need to have the slippage required, and some gravel roads are so good that they have limited ability for the tyres to slip, and then you’ll do damage.
4H should be used for high speed off road work, where the vehicle isn’t labouring at all. That means on hard beaches, or gravel roads, or easy tracks that you need to go over 40km/h on.
The only exception for 4H on bitumen is if you have a centre diff lock that can be disengaged.
When should you engage 4L?
4L uses a different set of gears, which will generally top out at about 40 – 50km/h. It is designed for maximum torque, and will dramatically reduce the load you put on your 4WD. Soft beaches, mud runs, rock crawling and anything slow should be done in 4WD.
On beaches you can get away with using 4H a lot of the time, but if you are loaded up, and your vehicle is working hard, or its really soft, you will work your vehicle much harder in 4H than 4L, and you shouldn’t be going over 40km/h anyway, so low is the best choice.
What are the benefits of being in 4WD off road?
Greater traction and safety
By having all 4 wheels driving, you have far better traction for accelerating and turning. This applies particularly on gravel and mud. Add a bit of water to a lot of gravel roads and you can be in serious trouble real fast in 2WD.
It’s much easier to lose control of a vehicle in 2WD than in 4WD.
More even tyre wear
When we did our trip on the Gibb River Road in 2015 I didn’t engage 4WD nearly as much as I should have, and the rear tyres got absolutely hammered. This is because they are doing all of the driving, and slip far more, causing much greater wear. If you engage 4WD then all 4 wheels are pulling the 4WD along, and they’ll all wear far more evenly.
Less track damage
The more traction you have, the less track damage you do. Sure, you can do a fair bit in 2WD, but you’ll do more damage using it, and that means the next person to come along will cop it.
When do you use 4WD? Is your vehicle constant 4WD, or part time?