Knowing your vehicle
The more you know about your vehicle the easier it will be to effect a safe descent in steep and potentially slippery terrain. Does it have a manual or automatic transmission? Does it have low-range reduction? Is it equipped with ABS? Does it have hill descent control and, if so, is it variable? Are diff locks fitted? How does the handbrake operate?
If you have the answers to all of these questions you’ll be able to extract the best possible performance from your four-wheel drive, giving you the best chance of making a safe descent without a mishap.
Judging the terrain
Before you begin your descent you need to know what’s ahead of you. If you’re unsure then you should probably hop out of your vehicle and do a recce on foot.
Check out how step the hill is, feel underfoot to judge how slippery the surface is and keep an eye out for any obstacles or deep ruts and holes that you might need to avoid.
If the terrain is particularly slippery, make sure you also take note of the camber of the track. In muddy conditions even a slightly off-camber track can see you and your vehicle spear off course for an unintended trip into the scrub.
Driving Down the hill
Preparing for the descent is important. In slippery terrain you should lower your tyre pressures. This will provide a longer tyre footprint and allow the tyre to more easily conform to the terrain, giving it a better chance of gaining purchase rather than sliding over it.
Assuming your vehicle has low range, engage it before you begin the descent. Depending on your 4x4, this may require you to come to a standstill and select neutral prior to engaging low range. Always start off in first gear; if you feel the need to speed up later on you can always shift up a gear, but shifting back down might not be possible if you’re going too fast.
If your vehicle is equipped with hill descent control, engage it prior to commencing the descent, and if it has a rear diff lock, this can also be beneficial when descending a steep hill, so activate it.
Once you’re ready to go, ease of the brakes and try to stay off them. Applying the brakes on a vehicle without ABS can cause the wheels to lock, in which case you won’t be able to steer. You need to rely on the vehicle’s engine braking and low-range gearing to retard your speed on the descent; this will allow you to retain steering control. In slippery terrain, such as on a wet and muddy track, you may even have to accelerate slightly to maintain steering control.
Many vehicles equipped with ABS brakes will also feature hill descent control, which will automatically modulate braking to retard your progress without locking up the wheels. On some vehicles you can adjust the hill descent control target speed using the ‘accelerate’ and ‘decelerate’ buttons on the cruise control.
As you’re making your decent you need to adapt to the changing terrain; if there’s a particularly steep section up ahead, slow down as much as possible before you descend it, or if there are defined wheel tracks (and they’re not too deep) make sure you stick to them. If the ruts look too deep you may have to straddle them, but be careful that you don’t slide into them.
As the terrain levels out, you can accelerate and shift up a gear or two, but be ready to slow down and engage a lower gear if the track resumes its descent.
Some of the steepest and most intimidating descents you’ll ever be likely to make will be on sand dunes. When driving in sand, approach crests with trepidation. Get out of the vehicle and have a look if you’re unsure of the terrain ahead of you.
Before descending a steep dune, select a low gear and accelerate over the crest. Don’t apply the brakes as this will cause the wheels to lock; use your throttle to modulate speed.
Always keep the vehicle pointed directly down the dune; if you drive across a dune you could end up on your roof.
Finally, accelerate prior to reaching the base of the dune; momentum is your friend when driving in sand and often some of the softest patches will be at the base of big dunes.
If you’re travelling in convoy, leave a good gap between your vehicle and the one on front. If the vehicle ahead of you stops for any reason, you’ll want to be sure that you can do likewise. Better still, stay in radio communication with the other vehicles in your convoy so you can be sure that the track ahead is clear. You’ll also be able to ask drivers ahead of you what the track conditions are like.
When descending steep tracks, keep an eye out for oncoming vehicles. If you can find somewhere safe to pull over, and you can slow down without fear of losing steering control, stop to the side and leave as much space as possible. The vehicle driving up the track will likely need to keep up momentum, and the driver will not want to stop halfway up a steep and slippery incline.
And don’t forget…
Once you’ve made a successful descent, don’t forget to select high range and disengage traction aids such as hill descent control and rear diff lock. And if you’re travelling in convoy let the vehicle behind you know that it’s safe for them to begin their descent.
When driving in steep country there’s always the possibility that you’ll have to reverse down a hill after a failed ascent.
If you’ve stalled a vehicle with a manual gearbox on a steep hill and there’s no chance of continuing your ascent, select low-range reverse, take your foot off the brake pedal and, when you’re ready, fire up the engine. Resist the temptation to put your foot on the brake pedal as the front wheels will lock up and you won’t be able to steer; rely instead on your vehicle’s engine braking and low-range gearing to maintain a safe descent speed.
Vehicles with an automatic transmission will not likely offer as good low-range gearing as their manual counterparts but you should still try to avoid braking where possible.
If your vehicle is not equipped with hill descent control, you may be able to use the park brake to help arrest speed. This is where it pays to know how your vehicle works; the park brake on some 4x4s works only on the rear wheels, leaving the front wheels free to spin so that steering is not affected, while others will have a transmission-mounted park brake that will work on all four wheels. Oh, and on some vehicles the park brake will work on the front wheels, which should never be relied upon slow you down on steep descents.