Four-wheel drive vehicles have become super popular over the last few years. Many have realized the 4WD to be the most practical vehicle offering a perfect balance between a reliable work truck during the week and a functional play-toy on the weekends. However, knowing how to drive a 4WD and when it is appropriate to engage 4×4 modes is of utmost importance since it can mean the difference between having a fun day in the mountain tracks or hundreds of dollars worth of damage later. This article will discuss how and when to use 4 wheel drive in different situations.
A part-time 4WD should always be driven in a 4H mode as soon as the driving surface becomes slippery and wheel traction is low. Modern sophisticated 4WD vehicles do not require you to stop completely before engaging 4H and can be safely done at speeds up to 60Mph. If you are in 2H where only the rear wheels are propelling the vehicle forward, the 4WD can safely be engaged which will transfer power to both front and rear axles.
Knowing which driving surfaces you can safely engage 4WD is very important to preserve your drivetrain comp[onents. When driving a part-time 4×4, what are the risks of driving on a high-traction surface like concrete or tarmac in 4H mode? This article will discuss the right time to engage and disengage 4WD mode and how to drive a 4WD under various challenging driving conditions.
When to engage 4 Wheel Drive mode
At the start of an off-road trip, while driving to your destination, one is usually required to cover some distances on the freeways first to get out of the city. When driving in the city with a part-time 4-wheel-drive you will want to keep the vehicle in 2H mode. This mode only utilizes the rear wheels to propel the vehicle forward and offers a good MPG range over the 4H mode. This is because 2H uses fewer drivetrain components to propel the vehicle.
Once you leave the tarmac/asphalt/bitumen and hit any gravel or sand tracks you want to engage 4H immediately. The 4H means the power of the vehicle will be split 50/50 between the front and rear axles giving the vehicle a more stable feel and more traction is gained since all 4 wheels are propelling the vehicle forward. The front wheels will pull and the rear wheels will push offering superior traction and stability over the 2H mode.
If you have a permanent 4WD vehicle you will not be required to do anything once you leave the tarmac and get onto the gravel roads since the vehicle is always in 4H mode. Part-time 4WD vehicles do not have a viscous coupling between the front and rear drive-shafts which allows them to rotate at different speeds when needed. For this reason, we cannon engage 4H on the tarmac with a part-time 4WD, since drive train windup will occur. It is only once we leave the tarmac or a high-traction surface where adequate slippage between front and rear wheels is present that we safely engage 4H, such as sand, gravel, grass, or snow driving surfaces.
If you would like to read more about drive-train windup – I wrote an article about it here.
When not to engage 4 wheel drive
For the purposes of this article, unless otherwise stated, we will always be referring to a part-time 4WD and not a permanent or full-time 4WD.
Do not engage 4H when you are driving under the following conditions:
- On the freeway when road surfaces are dry
- On cement when traction is good and surfaces are dry
- On a semi-slippery surface such as a partly snow covered tar road
- On a semi-slippery surface such as a partly wet tar road
- On winding roads where surface traction is good
- On any driving surface where wheel grip is good and the wheels cannot easily slip or lose traction
It is very important to understand the above since there is a major risk of causing major damage to your vehicle which could run into the hundreds of thousands to repair. When you engage the 4H on high traction surfaces the risk of “driveline binding” is massive. Drivetrain components will be at risk of failing and the 4WD system will begin to lock up.
This effect causes your vehicle to under-steer heavily, gears to get jammed, and makes steering very difficult and even jerky. This phenomenon is caused by the front wheels battling the rotational force coming from the front driveshaft as it tries to slow down the front wheels, causing the massive under-steer effect. You should avoid engaging 4WD on a high traction surface at all costs. The longer you drive in that mode, you risk serious damage to your drive-train components and you will find it increasingly difficult to remove it from 4WD mode and switch back to 2WD mode.
How to disengage 4WD mode
When driving in 4Hi on a slippery road and the surface changes to a tarmac road or any high-traction surface you need to remove the vehicle from the 4H mode. This is done by bringing the vehicle to a complete stop and placing the 4×4 dial or short ration gear lever back into 2H. Many modern 4WD vehicles are now equipped with a 4A option on the 4×4 Dial selector. This option – which can be found on the new Ram and Jeep Wranglers, for example, allows the vehicle to be driven in 4A which essentially is 4H or in the 2H mode without any risk. The 4A or Auto 4H mode allows the driver to leave the selection in 4A mode irrespective of the driving surface and the vehicle will take care of the rest.
When 4Lo is engaged, once again, the vehicle needs to be brought to a complete stop first before you can change the driving mode back to 4H or 2H once back on the tarmac. 4Lo is seldom used and should only be engaged when you cannot safely overcome an obstacle in 4H and high torque combined with slow controlled speed is required to do so.
If you would like to read more about 4Hi and 4Lo and when to use them – I wrote an article about it here.
Permanent 4WD vs Part-Time 4WD
Vehicles with part-time 4WD systems have differentials that are fitted to the front and rear axle assemblies. That is the big round bell housing you see underneath your truck and is the lowest part of your vehicle. When driving in 2H the power is transferred through the rear propeller shaft or driveshaft to the rear final drive and the differential gears and rear axle shaft. The gears in the rear differential allow the rear wheels to turn at different speeds when the vehicle turns left or right. While continuing to transfer equal torque to each wheel.
Understanding Part-time 4WD Systems
When 4WD is engaged by selecting 4H in a part-time 4-wheel-drive, the transfer case joins the front and rear driveshafts and transmits equal power to the front and rear axles via the two drive-shafts. The final drive is transmitted through both the front and rear axle assemblies which propels the wheels.
When turning, the swiveling effect caused by the front wheels creates a wider turning circle than the rear wheels and this, in turn, causes a difference in the rotational speeds between the front and rear wheels. This phenomenon results in a difference in rotational speeds of the front and rear propeller shafts (Driveshafts).
Due to the difference in speed between the inner and outer wheels, both axle shafts also turn at dissimilar speeds. Variances in speed can also be caused by uneven tire wear between the front and rear wheels or different inflation pressures.
Understanding Full-Time 4WD Systems
In a full-time 4WD system, power is permanently sent to all four wheels and they are always driven. Occasionally the power is sent equally and other times it varies due to low traction driving surface to cause variations in the rotational speeds of the front and rear wheels such as driving in snow, ice, sand, and mud, or when the vehicle is turning.
Contrary to popular belief a 4WD is only an advantage under acceleration and does not assist you with stopping or turning on slippery surfaces. Only outfitting your vehicle with good AT (All-terrain) tires will enhance your vehicle’s stopping and turning capabilities on low traction surfaces. This upgrade will also assist your vehicle with electronic stability and traction management systems.
Handling characteristics of a 4WD
Four-Wheel-Drives have very unique handling compared to smaller sedans, hatchbacks, and other monocoque chassis-type vehicles. The reason is the body on frame design and the higher center of gravity of a 4WD. When driving on the tarmac in 2H with a 4WD the vehicle will feel slightly top-heavy with a bit more body roll in corners than a normal vehicle. This is a side-effect or negative property of a ladder-frame chassis design where the body sits on top of the ladder frame chassis, unlike a car’s monocoque chassis where the vehicle’s framework and chassis is one complete molded structure.
If you would like to read more about ladder frame chassis vs monocoque – I wrote an article about it here.
The excessive weight of a ladder framed 4WD is a huge disadvantage when it comes to vehicle on-road performance and fuel efficiency. A 4WD vehicle’s mass and larger turning circle make turning in emergency maneuvers or parking in tight spaces challenging. The ladder frame is much heavier than monocoque, thus increasing fuel consumption and diminished performance compared to monocoque type vehicles.
The high center of gravity negatively impacts the vehicle’s cornering ability as there is excessive torsional flexing.
Breaking is weak due to the vehicle’s size and weight. Body roll can be reduced by upgrading the suspension to a stiffer setup, however, it will never be as crisp and direct as a monocoque chassis vehicle. Their lack of crumple zones and safety features in older ladder-frame vehicles reduces occupants’ safety.
Off Road Superiority
When conquering any off-road obstacle you will almost always opt for the ladder frame since he has such off-road prowess with its tough framework. They can literally take any terrain you can possibly throw at them. May that be rocks, gravel, sand, snow you name it, and while carrying a load. In this environment, the ladder frame comes into its own.
Ladder frame 4WD’s have a higher floor plan that increases the center of gravity due to its design. This allows the vehicle to boast higher ground clearance which is excellent for conquering off-road obstacles or handling any off-road challenges you throw at it.
How to drive Steep uneven hills
Steep uneven hills are best driven in 2nd gear 4Lo. This will give you the perfect balance between power and control with enough time to calculate your driving line as you progress upward. If the hill has many uneven deep ruts or loose gravel stones, then it would be best to engage your rear locker if your vehicle has one. This will allow both rear wheels to maintain traction even if one wheel becomes airborne or loses traction midway up the hill. Also, make sure your tire pressure is decreased to around 1.5bar to maintain maximum traction and control.
If your vehicle is not equipped with a rear differential locker but has TC (Traction Control) always ensure the TC is activated. In the event, the vehicle loses traction, refrain from slowing down but maintain a steady pressure of the gas pedal to allow the traction control to kick in once it detects that a wheel has lost grip. This could take a second or two to activate which is precious time when climbing steep hills. Allow the TC to take effect and keep the revs high enough so that in the event the slipping wheel does bite again, that your revs don’t drop, resulting in a stall. If your 4WD has a torque converter, maintain a constant rev to allow it to kick in and stay active all the way up the hill-climb.
Never speed up an uneven low traction hill since this will result in front body panel damage as well as undercarriage damage. Higher speeds at high power outputs could easily result in CV joint failure and suspension damage. Always maintain a slow but steady pace and try not to stop midway up a hill if possible. It is always a good practice to walk the hill first and choose your desired driveline before you attempt it.
How to drive down steep descents
Steep descents are best done slowly. As slow as possible and as fast as necessary. Traction is easily broken when traversing slippery or muddy mountain tracks and should be done with extreme caution. Always engage 4Lo and where sections get technical, engage your lockers. Use the lowest gearing possible to assist the engine braking to maintain full control at all times.
If you drive a modern 4WD that has hill descent control, activate it at the lowest speed first and slowly increase the speed where it’s safe to do so. Never depress the clutch to allow the vehicle to coast. Stay in gear at all times. Always scan the track ahead and carefully select the safest drive lines ahead of time.
Walk the track and scan the trail for the best driveline possible.
How to drive on gravel roads
Tire pressure is key here, so always ensure you decrease your tires to 1.5bar all around. Do not exceed speeds over 80km/h on gravel no matter how good visibility is and how far ahead up the road you can see. Even straight wide gravel roads should be driven with caution. Where possible, scan the left and right of the gravel roads and be on the lookout for wild game that could run in front of your vehicle at any time.
Maintain a safe speed below 80km/h and always scan the road ahead, more so than usual, for pot-holes and deep ruts in the road surface. Avoiding these is recommended if you want to avoid any punctures or sidewall damage.
Gravel or dirt roads can be fun to drive provided they are not filled with too many corrugations, also known as washboards since that is what it looks like. Badly corrugated roads can be very treacherous since the wheels never make 100% contact with the road surface at all times. Wash-boarding or corrugation of roads is formed by sequences of ripples, which happen when vehicles travel at speeds high enough that the wheels roll over or skim the road surface causing them to bounce.
If you are experiencing too much vibration from the corrugations that the ride becomes uncomfortable of your risk vehicle damage, it is advised to stop and decrease your tire pressure even more to about 1.2 bar to allow the tire to absorb more of the road surface irregularities. Try lowering your speed and driving within the tracks where you can notice most vehicles have driven before.
How to 4 wheel drive in snow
When snow wheeling you need to maintain enough momentum. It’s similar to driving in slippery mud or deep sand, except you don’t always feel the bottom surface. How you approach the snow is determined by the type of snow it is. There are times when a slow approach is needed and other times when you will need to hammer down and use lots of momentum to dig in, similar to when you are driving in mud. In order to know when to use the correct technique, you’ll need to develop the ability to “read” snow. We will talk more about that a bit later.
If you would like to read more about snow-wheeling and how to read snow – I wrote an article about it here.
So far we’ve determined, if the snow is soft and there is a firm bottom, not too deep down, you want to throttle down. Alternatively, if the snow is very soft and “fluffy” with no bottom in sight but it is packing firm, then you want to take a different approach. Decrease your tire pressure to anywhere between 2psi and 4psi and engage your lockers. Allow the snow to pack on the tires and keep the throttle steady because snow will stick to snow allowing you slow forward progression.
DO NOT dig down wherever possible and avoid churning up deep holes. Your natural reaction will be to power forward. If you lose momentum and forward progression stops, rather back up for a few feet and hit it again. This procedure might be slow going but it will definitely work in thick soft snow. Once you start digging holes, you are as good as stuck. If however, the snow is just a few inches deep, use the gas pedal and don’t be too concerned about the snow type too much.
How to 4 wheel drive in Mud
The first thing to do when going mudding is to decrease tire pressures to around 20-24 psi. Next, make sure your transfer case is in low range.
NB Make 100% sure your Traction Control (TC) is switched off. TC will apply brakes to the spinning wheels and you will quickly lose any forward momentum.
Always take the time to check the mud to ensure there are no dangerous obstacles lurking under muddy pools. Use a stick and have a poke around before you attempt to drive it. Also, poking around in the mud pools first will help you get a feel for how soft and deep the bottom of the muddy track is.
Make sure there are no logs or rocks below the surface that somebody has previously thrown in there for some extra traction. This could cause major damage to your sump, under-body, and other low-hanging components.
If you are driving an auto you want to make sure the sequential shift is selected and you are in 4Lo.
If you would like to read more about 4WD mudding techniques – I wrote an article about it here.
In a manual transmission, you want to select 1st or 2nd 4Lo and that depends on how tight the track is upfront. In most cases, there is always a set of ruts in front of you so don’t attempt to avoid them just drive straight into those muddy ruts as you will more than likely slip right into them anyway. The only exception to that rule is if the muddy ruts ahead are much deeper than your tires – then you will want to avoid them as much as possible. This is because deep muddy ruts that are deeper than your tires will only result in your vehicle “bellying up” anyway.
How to 4 wheel drive in Sand
Sand driving can be an exhilarating and fun experience if done correctly. Like most off-road driving conditions there are a few rules to adhere to. Nine times out of ten, you and your 4WD will do fine if you adhere to the following three guidelines.
- Air down your tires
- Use common sense
- Maintain momentum
That is the “secret formula” to driving on beach sand irrelevant to your vehicle brand. Maintain a steady forward momentum and you will be surprised what size dunes your vehicle can overcome.
Reducing tire pressure will have much less wear and tear on the components of your vehicle. Do not decrease your tire pressure too much because if you hit a bump, sand grains could get in between the tire bead and the rim and the rest of the air tends to leak out. Slightly larger tires tend to do a bit better in soft beach sand as it has a wider and longer footprint that distributes weight over a larger surface area. Bigger footprints give you more traction and a more aggressive AT tire helps too. If your tires are too aggressive the tread patterns will result in the wheels digging into the sand instead of floating over the top.
After driving on the warm sand for a few hours, stop and re-check your tire pressures as the sand resistance builds up heat inside the tire fairly quickly thus re-inflating the tire again.
It is important to monitor your engine temperature gauge after a few hours in the dunes as this is a high resistance terrain usually driven in high temperatures. Maintaining a steady pace ensures good operating temperature and better traction. There is always the potential risk of overheating your engine.
How to tackle deep ruts in 4WD
Engage 4Lo with your lockers engaged. Drive as slowly as possible but as steady as you can to create a bit of momentum since you will always have 1 or 2 wheels airborne at any given time so you want to ensure the momentum is enough to push the vehicle through allowing the diff lockers to work its magic.
If the vehicle loses traction, even with the lockers engaged, stop immediately and redo the obstacle with slightly more momentum this time. You need to almost “rock” the vehicle over each ditch or rut. Try and keep a smooth momentum going to lessen track damage with excess wheel spinning and slippage.
If you have no lockers, but only TC (traction control) it is recommended to maintain a slightly higher momentum, not allowing each wheel to drop into opposite ruts simultaneously. This will cause maximum loss of traction and excessive wheel spinning, ripping up the track and making it even more challenging for the vehicles coming behind you. Always try and keep at least 3 wheels grounded as much as possible when driving off-road ruts without lockers.
How to rock crawl with a 4WD
Rock crawling is a sport/hobby which requires you to carefully drive off-road over large rocks and technical terrain.
You need to traverse obstacles carefully and slowly while selecting the best drive-line. An experienced spotter is needed to guide the driver when doing extreme rock crawling as the driver’s visibility will be limited in most situations. When rock crawling always try to keep your tires on the high side if possible.
If you feel you can walk over an obstacle then you can definitely crawl over it with your 4×4. It’s helpful to have 2-way radio communication between the driver and the spotter to ensure audible directions from the spotter. The Driver should trust his spotter’s judgment 100% to avoid roll-overs and vehicle damage.
Sold front and rear axle vehicles like the Jeep Wrangler, Land Rover Defender, Toyota Land Cruisers, and Nissan Patrols are popular choices for rock crawling due to their superior flexing abilities. Solid Front Axle (SFA) vehicles have excellent flexing capabilities making them the popular choice over Independent Front Suspensions (IFS).
Upgraded suspensions with longer shock travel allow for increased flex along with large aggressive 35″ tires are ideal vehicle setups for rock crawling.
When to engage 4Lo
The 4 symbolized in “4-Lo” indicates that your vehicle is in 4 wheel drive mode, Low-range. This means all 4 wheels are being propelled forward at the axles by the engine via the transmission and transfer case. The “lo” represented in “4-Lo” indicates that low range mode has been engaged in the transfer box. Most off-road 4×4 vehicles have a 2H, 4H, and 4-Lo setting. Vehicles with 4-Lo are equipped with a transfer case that uses much lower gear ratios to utilize all the available power and torque of the vehicle easier. This low ratio keeps the revs higher and makes it harder to stall the vehicle when conquering challenging obstacles.
4-Lo mode allows the vehicle to overcome challenging terrain with more ease without placing undue strain on the gearbox, clutch, transfer case, and engine. Difficult terrain could be any of the following:
- Loose deep beach sand
- Thick mud
- Rock crawling
- Steep uneven low-traction Inclines
- Long technical declines
- Deep River crossings.
4-Lo uses shorter gear ratios, keeping the vehicle within the power range. Many people are under the impression that 4-Lo increases the torque of the vehicle, however, it does not increase but only utilizes the available torque better and quicker by keeping the vehicle in a higher rev-range and in the highest torque band of the vehicle. This ensures the vehicle’s power is readily available when needed.
When To Use 4 Hi And 4 Low?
Low-range or 4-Lo is a very powerful function of a 4WD and allows you to accomplish feats no 2WD ever could. You engage low-range to get you through soft sand, over tall sand dunes, up steep hills, and down difficult mountain tracks. It will even get you through deep mud or snow, and it’ll help you drive over boulders and deep ruts with ease. Use it wisely and your 4WD will, not only take you to many amazing places but also bring you back home safely. The lower gearing also improves your 4×4’s capabilities because it uses the vehicle’s engine braking, which helps to control your progress and speed going downhill. This allows for more controlled handling without placing all the stress on the brakes alone.
As mentioned earlier, 4-Lo is used only when you require optimal traction and absolute maximum power. This is only to be engaged when the terrain is really difficult and driving conditions forces you to lower your speed and gear selection down to 1st or 2nd gear. Extreme rock crawling when you need to negotiate each obstacle slowly and precisely will call for 4-Lo. Driving through thick loose beach sand with a load will require 4-Lo to prevent damage to your vehicle’s clutch or to decrease the risk of overheating the gearbox if you are driving an automatic 4 wheel drive vehicle. When doing any deep river crossings you are better off engaging 4-lo to ensure you are getting optimum traction and using the power available to you sufficiently.
Each and every off-road situation or obstacle needs to be carefully calculated and assessed by you before you decide to take it on. However, a good rule of thumb is always to judge the speed vs the difficulty you are required to succeed. Always remember “As slow as possible and as fast and necessary”, no more, no less. Generally, if you cannot engage 4-Hi 2nd or 3rd gear to cross an obstacle or if you feel the obstacle will place too much mechanical stress on your vehicle then you are better off engaging 4-lo and rather take it slow and steady.
“As slow as possible, as fast as necessary”
Always ensure you keep the risk of vehicle damage to an absolute minimum. This will mean you will at times have to exit your vehicle and walk the terrain or the obstacle first to determine the best driving line and if there is any risk of stalling or if a roll-back or even a rollover is a possibility. This is something you want to avoid at all costs. It is best to be safe than sorry and I always say, if you have the functionality on your vehicle, use it.
How to drive a 4WD on the beach
Always try and aim for more densely packed or damp sand on the beaches. This is good for both the environment and vehicle stability. Always scan sand terrain ahead as sand tracks can get really bumpy and uneven from dirt bikes and ATV’s churning up the sand.
Sand Dune driving tips
- To clear a decent size dune you will need speed and momentum on your side else you will not make the dune.
- Make sure you check out the bottom or base of the dune for a good approach ramp so you don’t nosedive straight into the dune and lose all your momentum from your run-up
- Nose-diving into a steep dune doesn’t feel great at all and you risk seriously damaging yourself and your Jeep suspension.
- Stay on the throttle till you reach the top of the dune and tap off just before the apex and let the momentum and light throttle carry you over gently
- To master this art takes some practice and you need to be able to judge where the top of the dune is to know when to tap off the gas.
- Tap off the gas too soon and you won’t make all the way up the dune. Tap off too late and you’ll go flying over the dune and nose-diving over the other side.
- If you do not have visibility of what is on the other side of the dune then turn off to the side of the dune just before the apex and ride the top of the dune first.
- NB: If you don’t let-off before the dune apex you will get air-borne and cause massive damage and injury to yourself and your precious Jeep
- When your Jeep comes to a dead stop midway up a dude, take your foot off the gas, pop it in reverse and drive out of the sand and retry the dune, this time, with more speed and momentum
- Remember to always keep the vehicle straight when reversing down a high sand dune
- Always carry a recovery strap and shackles with you, especially if running beaches that are less traveled and secluded
- Have a driving buddy with you, if at all possible.
Conclusion
4-Wheel-Drive vehicles are loads of fun to drive if you know how and when to use the correct gear selection and when to engage 4Lo. Knowing your vehicle’s power band and how it behaves is a very important aspect when tackling challenging off-road obstacles. In almost all cases, your tire pressure will play a major part in the success of your 4WD abilities.
Never attempt any obstacle at high speed
and always consider the environment and other 4WD vehicles coming behind you.
Avoid excessive wheel spinning and ripping up of tracks where possible. Respect
your vehicle and the environment at all times.
Practice makes perfect, so get out there and enjoy your 4WD!