Welcome to 4×4 Africa’s 4×4 Articles and 4×4 Technical
At 4×4 Africa you will find basic information as well as in depth articles on a variety of 4×4 and Africa related topics. It is a work in progress, therefore keep coming back to these pages and see what new articles have been added to the 4×4 Articles and How-To section. The information contained in these pages will be a guide to the novice as well as the seasoned 4WD owner. As with any manual or information; unless tried in person and put to the test, it will always only be theory. Therefore use the info on Four Wheel Driving, as a guide to hone our own style of driving………….. and have fun.
How does a 4×4 Vehicle work
Most cars make use of either Rear Wheel Drive or Front Wheel Drive, but becoming increasing popular are All Wheel Drive vehicles, also known as Permanent 4WD or Full Time 4WD. Also part of the 4WD family, are Standby 4WD and our favourite, the Part-time 4×4. Stan
dby 4×4 is a vehicle that is usually a 2WD or 2×4 and will automatically select 4WD when necessary. Standby or Part-time 4×4 is also 2×4 till the driver decides to engage 4×4, either by pushing a button, turning a selector or engaging a lever. Four Wheel Drive is engaged by locking the front and rear differential via the transfer case. Four Wheel Drives that utilise a mechanical lever to lock the transfer also make popular Africa Overland vehicles due to its simplicity and robustness.
With AWD and Permanent 4 Wheel Drive vehicles, no or very little driver input is required in regards to 4×4, with the exception of maybe selecting Low Range if your vehicle is equipped with L4. Most Part Time 4×4 cars have a selection between H4 (High Range) and L4 (Low Range). With the selection of L4, the Centre Differential is locked, even in a Permanent 4×4, and equal drive is send to the front and rear differential. L4 is the gear to use when you want to run with the big boys or getting into the “Tough Stuff”.
How to shift from 2 Wheel to 4 Wheel Drive
The general rule of shifting from 2 Wheel Drive to 4WD is to slow the car down or even coming to a standstill before selecting 4WD. Most modern cars allow the selection of 4×4 at reasonable cruising speeds, but always consult the owners manual first. When selecting Low range, L4, it is best to only do so when the vehicle is parked. When H4 or L4 is selected, an indicator lamp light will confirm when it is engaged, and the opposite when it is disengaged. Do not rely on the indicator lights, as lamps can fail; know your vehicle and you will be able to tell in what drive you are.
Free-Wheel Hubs
Free-Wheel Hubs are found on some selectable 4×4’s. A part-time 4×4 will stay a 2×4 even when 4WD is selected for as long as the front Free-Wheel hubs are not engaged. Selection is made by one of three methods: 1. Manual: Rotate a dial on both front wheels to the “lock” position.
2. Automatic: The hubs are locked when the vehicle is shifted to 4WD
3. Power Hub Locking: By pushing or turning a switch the hubs are locked. Some vehicles require to be in Reverse for the lock to be engaged, therefore select the Hub Lock BEFORE the obstacle, as it might not be possible once stuck.
Limited Slip and Differential Lock Systems
Limited Slip Diff, LSD: Some Off-road vehicles are equipped with LSD, but not so common with newer vehicles. It work by restricting one wheel spin, but not completely locking it up. When one wheel is forced to rotate faster than the other, as in cornering it will act as a normal open diff. Limited Slip Diffs are a good compromise between a positive locked and open diff, but does require more maintenance.
Differential Locks, Diff Locks, Lockers: Some offroad and most 4×4 bakkies in South Africa are equipped with a rear locker. Diff locks are used when one wheel on the same axle looses traction and starts to spin, leaving the other wheel motionless, or without drive. Diff locks are only to be used in off-road conditions and in a straight line, as cornering with lockers engaged, especially the front locker is very difficult. A twin locked “4by” with a flexing suspension and mud terrain tyres is a beast and something many true 4WD owner dreams about.
Tight Corner Braking Phenomenon
Driving a vehicle with the centre differential locked, and making a tight turn, can make the car feel as if it is blocked, this is due to the difference in speed required between the front and rear wheels to make the sharp turn. It is not something to be scared of but should be avoided on hard sealed roads as it will result in worn tyres and drive-train.
Basics of Off-road Driving
Two Wheel Drive, 2WD, H2: Use this drive position for Sealed roads, Hard surfaces, absence of ruts and adverse inclines and also in situations where wheel-spin is unlikely to occur. 2WD is better for wear on the drive train and tyres, and save an fuel consumption too.
Four Wheel Drive, 4×4, 4WD, H4: Also known as High speed 4WD, is used for normal driving on slippery surfaces like: ice, snow, sand other than deep sand, but also vehicle vehicle depending. Engaging 4×4 on dirt roads can also be a safer option than 2 Wheel Drive. By using 4WD, greater traction is provided, therefore less strain for forward movement and reduced wheel spin.
Low Range, L4: This is the range position why some of us buy an off-road vehicle; used for maximum traction and power. Use L4 for off-road driving, deep sand, mud, deep snow, hill climbing and steep hill descending. Use L4 for when driving over large rocks and wherever very slow speeds are required to avoid damage to your vehicle.
Driving Techniques
Below are some of the off-road conditions you can come across; what to look out for and the better gear selection is for the obstacle. This should only seen as a guideline as vehicle, vehicle set-up, tyres, performance and driver experience are either assisting or not. Tyre pressure can be the single most limiting or beneficial traction aid in all the obstacles you will come across, therefore pay careful attention to those pressures. Choosing the correct line and approach can make an obstacle easier or impassable. For a more in-depth discussion on driving techniques, follow the below links.
Sand Driving: Look if the sand is dry or wet, fine or course, Gradient/Slope, what is the distance to cross.
= Select L4, 2nd Gear to H4, 1st Gear.
Mud Driving: Look for: depth of the sloppy stuff, existing tracks, type of mud (clay, sandy, …), Gradient, Side Slope, crossing distance, side drop-off.
= Select L4 for deep mud and H4, lower gear for the rest and be very mindful of stopping distances.
Rock Crawling: Look for: Under carriage and differential clearances, pick the easiest line and avoid vehicle damage.
= Select L4 and the slowest speed without hampering forward motion.
Hill climb: Look for: gradient, side slope, side drop-off, slipperiness, distance to the top, crest angle and what is on the other side.
= Select a gear that will not require a gear shift till on top.
Down Hill Drive: Look for: Decline/Angle, Surface condition, Length, Side-slope, existing ruts.
= Choose a lower gear that require fewer brake input (engine braking), but not so slow that causes steering loss due to front wheel slipping.
Water Crossing: Look for: Water depth, Bottom surface type (sandy, muddy, obstacles), Rate of water flow, Distance to cross,
= Select: L4, do not rush into the water and proceed at a pace that can push a bow-wave in-front of the 4×4.
Driving in Snow: Look for: Depth of snow, Bottom conditions (sand, clay, ice, possible obstacles), Gradient
= Select a higher gear for take-off (avoid wheel-spin). Lower gear down hill and watch for steering loss.
