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Low range gearing - Do you need it?

 

The arrival of a version of Hyundai’s Santa Fe with only front-wheel drive rather than all-wheel drive underscores the gradual movement of SUVs from their 4WD roots.

The Santa Fe joins a growing number of SUVs that offer the option of two-wheel drive, including Ford’s Territory and the Toyota Highlander.

This “less is more” philosophy is customer-driven. Why have all-wheel drive if a section of the marketplace doesn’t want it?

The same thing happened with this week’s topic. Low-range gearing was once found on every 4WD vehicle, but has vanished from most “soft” SUVs.

The role of low-range gearing continues to confuse some people.

If your SUV doesn’t have it, are you missing out on something?

If you do have it, have you ever used it? Do you even know what it’s for?

Everyone knows that first gear in a passenger vehicle provides plenty of “pulling power” and is slow enough to creep along when necessary.

Off-road, drivers often need good pulling power and to be able to drive very slowly under full control, but conventional gearing is too “tall” for these special conditions.

They also need to be able to descend steep slopes slowly without being overly reliant on the brakes.

The solution was to put extra reduction gearing between the gearbox and the driveshafts that could be engaged and disengaged as required.

Most low-range gearing at least doubles the conventional ratios, providing massive stump-pulling torque as well as the ability to crawl along at the pace of a lethargic tortoise.

A typical SUV without low-range gearing may have an overall low ratio (the ratio of first gear multiplied by the differential ratio) of around 17:1.

A 4WD with a good low ratio will be something like 45:1 with a few around 60:1, which is overkill for most situations, unless you have a thing about crawling over rocks.

Low-range can also be good for heavy towing at low speed. But as true 4WDs increasingly became on-road station wagon substitutes, low-range gearing became less important. To many 4WD buyers, it was no more than extra unnecessary weight, its presence identified by that funny extra lever sticking out from the floor.

Those who prepare used Japanese imports for sale here all tell stories of changing oil in the transfer case that holds the extra gearing and finding it in like-new condition, a clear indicator that the gears had rarely if ever been engaged.

So when the “soft off-roaders” first appeared, their designers did the obvious thing – they left out the low-range gearing.

Nobody minded and vehicles like the Toyota RAV4 went on to become hugely successful.

Electronics have helped overcome some of the disadvantages of not having low-range gearing.

For example, hill descent control – pioneered by Land Rover on the original Freelander and now widely used – helps vehicles down steep slopes as well as, or better than, any super-low gear could.

As long as vehicles need to be used off-road, whether on farms, in forests or around construction sites, there’ll always be a need for low-range gearing, but for most of today’s SUV buyers its absence will never be missed, just as all-wheel drive won’t usually be missed by those who buy 2WD versions of some of our most popular “off-roaders”.


Auto Trader New Zealand