A lot of 4WD’s operate in 2WD for majority of their life, and to get the front two wheels to drive you have to engage 4WD. This can be done in a variety of ways, but the original way was with manual locking hubs. Some 4WD’s are constant 4WD, and just lock a centre differential as needed to get to 4WD high range.
However, there are many 4WD’s today that can go from 2WD (or AWD) to 4WD high range by just turning a dial, or pressing a button. Our Isuzu Dmax has the ability to swap between 2WD and 4WD high range at any speed between 0 and 100km/h, and this is known as a shift on the fly 4WD.
I can’t tell you of how useful this, coming from a Hilux and Land Cruiser, that required you to get out and manually lock hubs, and be stationary or really slow moving when you change.
Ultimately, what this meant was that I often didn’t put it in 4WD when it should have been, purely because I didn’t want to pull up to a stop, engage 4WD and then get going again. Gravel roads for example, often were done in 2WD instead of 4WD, which meant less traction, and more wear on the tyres.
The rear tyres on my Land Cruiser were substantially further worn than the fronts after a 9000km trip to the Kimberley, purely because the rear wheels were pushing 3 tonnes of 4WD up and over nasty gravel roads, without the assistance of the front wheel.
With the Isuzu Dmax now, you just turn a knob as soon as you go onto any other terrain than real hard gravel or bitumen, and a few seconds later 4WD is engaged. It makes things a breeze, as I no longer have to stop even for half a second to engage 4WD. Now, every gravel road is driven in 4WD, which is safer, better for the 4WD and reduces the tyre wear!
When should you use 4WD high range?
For high speed driving, high range is the perfect choice. This includes driving on gravel, or surfaces that are uneven and slippery. You should never be in 4WD on a bitumen road, unless its constant 4WD with the centre diff lock engaged.
When should you use 4WD low range?
Low range on the other hand is used for slow, high torque applications. This means rock crawling, mud and most beach driving (unless its like concrete). To get to low range you do have to come to a complete stop, and many 4WD’s require you to be in neutral as well.
This is less of an issue, as you usually come to a stop before needing low range anyway!
For us, a shift on the fly 4WD is mainly useful when coming on and off gravel roads often, and not having to stop at all.
How do you engage 4WD? Would you love to have 4WD on the fly?