What’s so important about low range in an all-wheel drive? We have the answers right here.
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We were asked:
What is the difference between high-range and low-range four-wheel drive?
It’s often considered the most important element of an off-roader: a decent low-end transfer case. It used to be easy to spot by the short lever next to the shifter. Today, you often need to look for a dial, knob, or switch.
Nostalgia aside, the bottom line is the same. A low-range transfer case—something like an auxiliary gearbox behind your actual transmission—is a strong ally for an off-roader.
In a broader sense, a transfer case’s job is to send drive forward and backward, converting two-wheel drive to four-wheel drive.
Some transfer cases are referred to as single-range because they do not provide additional low-range reduction. Dual range transfer cases offer two gear sets: high and low range. This would be the case with most four-wheel drive vehicles.
And of course there is an important difference between all-wheel drive and all-wheel drive. See this story for more information.
But back to this case. In high range, a transfer case directs drive forward and reverse without changing the transmission.
Choosing the low range engages an extra set of reduction gears, effectively reducing the vehicle’s overall ratio.
So, at the same engine RPMs in the same gear, your vehicle will be traveling at a much lower speed.
What is less obvious in this case, and more important for off-road use, is that the torque delivered to the wheels (which is multiplied by the gears) is vastly improved.
Try going up a hill, over a boulder or a steep sand dune (like in the picture above) and you’ll find that the motor won’t work or shake and you’ll have significantly more control and confidence from behind the bike.
The most capable – and most controllable – off-roaders always have a low gear ratio available for off-road driving, most commonly found in the transfer case.
It’s a little confusing, but lower gearing is represented by a higher gear number.
For example, the Jeep Wrangler Rubicon and Gladiator Rubicon have a transfer case with a 4:1 gear ratio, which is a significant jump from the 2.72:1 ratio found on non-Rubicon variants. Combine that with a low first gear and 4.1:1 diff gears and you have an overall gear ratio of 77:1.
Most 4WD Utes have an overall gear ratio of around 30-35:1, which is good enough for most standard 4WDs. However, more technical and demanding challenges will benefit from less overall reduction, either through a factory setup or serious aftermarket modifications.
Do you have a question about your next set of wheels or simply need car advice? No query is too big, small or obscure! Call the radio show (Trent on 2GB Sydney 1:30pm Monday and 9:00pm Wednesday, 5AA South Australia 1:30pm Tuesday and James on 3AW Melbourne 9:00pm every Thursday)or email us here: firstname.lastname@example.org.
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