It’s long been a benchmark of what makes a proper four-wheel-drive, but a low-range transfer case is still seen as one of the most important features.
It’s an old-school technology solution, essentially an additional two-speed gearbox within the driveline that is yet to be bettered by anything else software-based.
Low-range used to be an additional gear lever. Short and stubby, sitting near your regular gear stick, and needing an almighty yank and clunk to engage.
These days, it's often a button to press or a dial to twist to unlock a new dimension of off-road capability. More civilised, but less romantic.
What does low-range actually do?
What low-range does is provide a significant reduction in your overall gearing. Put simply, first gear in high-range might see a maximum speed of 20km/h before the engine speed hits redline.
With low-range engaged, this number drops dramatically to as low as 5km/h or 7km/h.
In other words, for the same given engine speed, you’re travelling much, much slower.
Going faster is better on a road or racetrack, of course, but going slower is actually a huge advantage for off-road driving. Let me explain.
Firstly, having a four-wheel-drive in low-range affords you significantly better control from behind the wheel. Slower speeds mean you’ve got more time to think about what you’re doing.
Wheel placement, choosing a line, and managing how much grip you have underfoot. This all takes time for the driver to compute, and more time is better.
And instead of travelling at around 5km/h at idle – which is way too fast in many off-road situations – doing around 2km/h or less is much better.
Speed plus time equals... something, something. Sorry, I found it really hard to pay attention during physics class.
But I do know this. As much as your vehicle speed is divided by the gearing reduction in low-range, it is also by that much your torque at the wheels is multiplied.
In other words, you’re trading speed for torque. Pace for brawny, twisting force. And off-road, that’s extremely good news.
All of a sudden, you’re not stalling or wincing over rocks and up climbs. Instead, the healthy supply of torque means the engine can take it all in its stride.
The maths of multiplication
But wait, it doesn’t stop there. Have you seen those videos of old Land Rover and Toyota four-wheel-drives pulling impossibly large and heavy vehicles. No, it’s not AI-generated.
Yes, these old four-wheel-drives have relatively underpowered powertrains, but the torque multiplication within the driveline generates the pulling power for serious work.
First and second gears in the main gearbox have their own level of reduction, and differentials offer another dose of torque multiplication as well.
First gear has a 3.6:1 ratio, which means it takes 3.6 full rotations of the engine to turn the wheel. A reduction in speed, and a commensurate increase in torque.
The differentials of an Isuzu D-Max give a set reduction of 3.727:1, which is often known as the final drive ratio.
And finally, the low-range transfer case can swap between 1:1 (no reduction) and 2.482:1.
And because they all multiply on top of each other, we end up with an overall reduction of 33.3:1.
That means it takes that many full rotations of the engine to turn the wheel once.
And when you consider there is 450Nm of torque being generated at the flywheel of the 3.0-litre four-cylinder diesel engine in the D-Max, the torque multiplication means 15,000Nm being delivered at the wheels (approximately).
We’ve spoken about the shortcomings of the BYD Shark in this case before, despite the fact that this plug-in hybrid ute has loads of torque available on paper.
What is this popular ute lacking? That wonderful torque multiplication of low-range.
Do I need low-range in my four-wheel-drive?
If you’re only taking on relatively minor and basic off-road challenges, then probably not. But if you’ve got aspirations for tougher tracks, then I would say low-range is mandatory. It makes your four-wheel-drive better, but it also makes you a better driver.
There’s less mechanical wear and tear on your pride and joy, and probably less spinning of wheels tearing up the track.
Sam Purcell has been writing about cars, four-wheel driving and camping since 2013, and obsessed with anything that goes brum-brum longer than he can remember. Sam joined the team at CarAdvice/Drive as the off-road Editor in 2018, after cutting his teeth at Unsealed 4X4 and Pat Callinan’s 4X4 Adventures. Off-road writer of the Year, Winner - Sam Purcell
