Kedah 4x4

In 2WD the traction (resistance) of only two wheels is used for forward movement. The other two tires have traction as well, but they are just rolling along. In rear wheel drive vehicles the front tires' traction is used to steer the vehicle. If more torque is applied than there is traction available, the 2 tires will break lose and start spinning. Once the tires are spinning, we say "we lost traction". So, if in need of more power/torque to move more weight or to go faster more traction is needed.

That can be achieved by sending some of the torque to the other two wheels (4WD) and using their traction as well. So, in 2WD torque is equally applied on 2 tires and the traction of those two tires has the burden of supporting the engine's power - each powered tire has deal with 50% of the available torque.

In 4WD torque is directed towards 4 tires. In 4WD the traction at each powered tire has to deal only with 25% of the torque created by engine, transmission, transfer case, and axle. Since each tire in 4WD has to carry a much smaller torque load (25% instead of 50%), it is much much less likely for the tires to break lose. That is why a 4WD can climb much steeper grades than a 2WD.

4WD was invented to use the traction of all 4 tires to either move more weight or drive on surfaces with marginal traction, or both without wheel spin.

Historians seem not certain who invented four wheel drive. According to what I found on the internet, the first 4WD vehicle was designed by Ferdinand Porsche (the founder of Porsche cars) for the Austrian truck manufacturer Jacob Lohner in 1900. The first vehicle in the history of 4WD had electric hub motors on each wheel - the engine powered a generator for power supply.

First mechanical 4WD (transfer case, drive shafts etc.) was built by the Dutch company Jacobus Spyker in 1902. Since the Lohner/Porsche four wheel drive has such an unusual status with its electric hub motors the Spyker should be considered the world's first four wheel drive.

The world's first automaker, Daimler Benz has a solid place in 4WD history as well. Mercedes started building 4WD vehicles 1903 - some of them already with all wheel steering.

The first US four wheel drive vehicle, was built 1911 by the Four Wheel Drive auto company (FWD).

1 flange (attaches to drive shaft), 2 pinion gear, spider gears, 4 ring gear, 5 left axle shaft, 6 right axle shaft

Here is what a differential is supposed to do: Always distribute equal amounts of torque to both wheels - always react to resistance (traction) to allow a wheel with more resistance to rotate less and a wheel with less resistance rotate more (needed in turns where the inside has to rotate less than the outside wheel). The rpm difference created by the diffrential is always proportional. If the inside tire rotates 15 rpm less in a turn than going straight - then the outside tire will rotate 15 rpm more than going straight.

To Lock:

· Bring the vehicle to stop

· Engage 4H (transfer shift lever)

· Resume driving – the hub is now locked

To Unlock:

· Bring the vehicle to stop

· Moves to 2H

· Reverse slowly (straight back for 2 meters)

· The hub automatically unlock – resume driving.

In 2WD with locking hubs disengaged rear drive shaft, rear differential and rear axle are rotating. Front tires are rolling along - only rear tires are pulling.

In 2WD with locking hubs engaged front drive shaft, front diff and front axle, rear drive shaft, rear diff and rear axle are rotating. Front tires are rolling along (since connected to the axle, they make the front drive line parts rotate) - only rear tires are pulling.

In 4WD with hubs disengaged front drive shaft, front diff and front axle, rear drive shaft, rear diff and rear axle are rotating. Front tires are rolling along (the transfer case makes the front drive line parts rotate, but since the wheels are disconnected the powerflow does not reach the tires) - rear tires are pulling.

In 4WD with hubs engaged front drive shaft, front diff and front axle, rear drive shaft, rear diff and rear axle are rotating. Front tires are pulling - rear tires are pulling.

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			Automatic Locking Hub
	Manual Free Wheeling Hub

If the vehicle is equipped with free wheeling hub, they are located on the two front wheels. Ensure that the free wheeling hub is set at “LOCK” position when the shift lever is in either “4H” position or the “4L” position. This is to ensure that the drive power is transmitted to the front wheels.

For automatic locking hub fitted vehicle, the hubs are automatically locked or unlocked according to the position of the transfer shift lever during driving.

Automatic Locking Hub

To Lock:

· Bring the vehicle to stop

· Engage 4H (transfer shift lever)

· Resume driving – the hub is now locked

To Unlock:

· Bring the vehicle to stop

· Moves to 2H

· Reverse slowly (straight back for 2 meters)

· The hub automatically unlock – resume driving.

Here is how you use your pt 4WD vehicle most efficiently:

· Drive in 2WD most of the time (that's where the name "part time" is coming from - you use 4WD only part of the time)

· Shift only into 4WD (don't forget to lock your hubs - if you have them) when you encounter snow, ice, or a rain slick road (if you have manual hubs keep them connected during the entire bad weather season).

· Shift back into 2WD as soon as you encounter dry surface (pretty much all vehicles now have "shift on the fly" that allows shifting without stopping)

· You may even want to shift back to 2WD while still on snow - because some vehicles display a binding effect even on snow.

· If you encounter turns while in 4WD just know that the steering will not be as crisp as in 2WD (understeer will occur - the turn might be a little wider than planned)

· Please be aware that ABS does not work properly with part time 4WD

· Make sure the bed (if you own a pickup) carries about as much weight as the front (especially valid when using 2WD - because the rear is powered and has, because of the empty bed, the least traction of both axles). More weight = more traction

For off-road use part time 4WD system is perfect.

Preparation

To drive safely Off-Road you don’t need big tires or suspension lifts, a winch is generally just dead weight and all the recovery kit in the world is just going to make you sink deeper in the mire. The most important piece of equipment you need is a reliable, well-serviced and well-maintained vehicle – and please note, dear reader it doesn’t really matter what make it is, every make of vehicle has its good and bad points. Driving Off Road will require you to halve, if not quarter, the time between service intervals, it also requires daily vehicle inspections. Buy a Haynes manual (if available) and read it – then find a reliable local garage or vehicle specialist and get to know them, find out if they will give discounts for regular work.

The next most important piece of equipment is a decent pair of boots. These need to be strong and waterproof and as well as being pliable enough to drive in, they must also be comfortable enough to walk fair distances in.

Third on the list is a sensible attitude towards yourself; your vehicle, its passengers and the area you are driving in and remember you don’t have to drive it.

Find the handbook for your vehicle and read it, learn as much as possible about your vehicle and its characteristics, for example its height and width are just as important as its wheelbase. This can be found when green laning on Exmoor, a fully prepared ’90 will simply not fit down some lanes whereas a long wheel base Samurai will be laughing all the way to the pub.

Note the front and rear overhangs and mark the line of the differentials with two pieces of tape, one on the bonnet and one in line on the dash. Spend time underneath your vehicle (with the engine off and the handbrake on, with the wheels chocked) looking for the low points and the vulnerable points.

Water Crossings

Water crossings can provide some of the most exhilarating and challenging 4WDriving around.

A 4WD is not an amphibious vehicle, in fact they are not even waterproof. The actual depth that you can cross depends on your vehicle.

As a general rule, if its above the top of your wheels its probably too deep.

Prior to a water crossing, it is a good idea to place your recovery gear on top of other luggage. The last thing you want to do is be searching under your cooler, tents and baggage for your recovery gear when you are stuck in the middle of a crossing.

Vehicle Preparation

The first thing to do before any unfamiliar water crossing is to walk it. If you cannot walk it you cannot cross it. If the water is flowing too quickly to safely walk the crossing, then it cannot be driven across.

Air Intake

Water and engines do not mix very well, and when they do it almost always results in bent pistons, valves and crankshaft commonly called "hydo-locking". The positioning of the air intake is critical to how well a vehicle can handle a crossing. For example certain Toyota models have their air intake directly behind the headlight, which is great to allow cold air into the engine but unfortunately is equally as great in directing water into the engine (An easy fix for this is to remove the plastic tubing from the air cleaner to the headlight when crossing water).

NEVER attempt a water crossing where the water depth is above the air intake height. If you intend doing regular water crossings, its a good idea to fit a snorkel as it raises the air intake to your roofline. It doesn't mean you can use your 4WD as a submarine!

Diesel vehicles are usually better for water crossings as you do not have the ignition system to worry about. Water in the ignition system usually results in a stalled engine and not actual engine damage, though this is of little comfort when you find yourself stuck in the middle of a crossing. Depending on the water depth, its advisable to climb out of your window rather than open the door and flood your carpets. To minimize stalling from a wet ignition, it’s a good idea to spray all the ignition system with water repellent beforehand.

Walking the Crossing

When walking your water crossings its best to walk in the intended wheel tracks to find if there are any hidden rocks or potholes, as well as for checking the depth. Potholes at common crossings are often caused by previous vehicles spinning their wheels after hitting a submerged rock. So if you find a pothole, check for submerged rocks. It’s a good idea to place markers at these points so you can avoid them. Its been known for a vehicle attempting a relatively easy crossing to suck in water when a single pothole has caused the hood to momentarily dip below the water level, causing water to enter the air intake, resulting in hydro-lock and a damaged engine.

Driving Technique

With a mental picture of your route, or better still, with markers in place, and all your vehicle preparation done, its time to start the crossing. Before you enter the water, remember to take off your seat belt and wind down your window.

Using low range second gear at 1500-2000 rpm (for most vehicles) creates just the right bow wave. Its important to get the speed just right as too fast will send water everywhere while too slow may flood the engine bay. Hopefully you follow your markers and get to the other side with no problems. But if you do strike problems avoid using the clutch as this may allow water to get between the friction plate and the flywheel, resulting in limited drive.

If the wheels start to slip, its important not to over-rev the engine but back-off the accelerator and hope the wheels regain traction. Excessive wheel-spin will not help.

If the engine stalls, put the vehicle in neutral without using the clutch and attempt to restart. If luck is on your side the engine will fire up. Now is not a good time to wish you had already disconnected the fan belt, as your engine bay will be flooded. Its normally best to use 1st gear low range and with a minimum of clutch usage, try and extricate yourself from this predicament.

Maintenance after Water-crossings

So once you have successfully crossed to the other side and are on your way home, you don't need to give the water crossing a second thought, right? Wrong! Any crossing at axle depth or deeper necessitates a checking of the diff oil for water contamination. Having an extended diff breather is not a 100% guarantee of waterproof ness and any crossing above your axles without extended cliff breathers should mean a mandatory inspection.

Checking your diffs for water contamination is very easy. Since water is heavier than oil, it will collect at the lowest point in the diff, right where the drain plug is located. After allowing time for your vehicle to cool, just loosen the drain bolt and run a small amount (~20mls) of the diff oil into a glass. If you're unlucky enough to have water present, the diff oil should be drained. It is best to flush the diff several times to ensure all traces of water are removed. Milky colored oil also indicates water is present and should also be changed.

If you're like the majority of 4WDrivers, you won't be able to change the diff oil until you get home, because you won't have spare oil and a sump pump to change it. If you suspect contaminated oil (a deep water crossing without extended diff breathers or perhaps you have leaking diff seals) then you can try and remove the water by draining the diff until only oil comes out the drain hole. Do not drain too much and leave your diff short of lubrication. Collect this oil and water emulsion as you should never dispose of oil into the environment. Save it till you get back home and dispose of it properly.

Its not only diffs that can have water contamination, but also your gearbox, transfer case and engine oil. However, it is usually only when a vehicle is stationary in deep water that these components are contaminated.

Amongst other items to check are bar mounted electric winches. These components may not be used for extended periods and when they're needed you may find they have seized up. If the winch has been submerged in water it is advisable to strip it and grease it accordingly. A quick operation of it after a crossing may prove it still works, but you may find out when it seizes that you washed all the grease out 6 months ago!

A water crossing is something that should not be taken too lightly as it has the potential to do expensive engine and drive-train damage. However, with the right vehicle preparation and post crossing maintenance, you can enjoy some of the most challenging 4WDriving around.

Water crossing Summary

· Vehicle Preparation

o Walk the crossing to check its depth.

o Don't cross fast flowing water.

o Place markers at hidden obstacles.

o Place a tarp across the front of the vehicle.

o Disconnect the fan belt if a viscous coupling fan is not fitted.

o Spray water repellent on distributor and ignition wires.

o Pack recovery gear on top, ready for use.

· Driving Technique

o Take off seat belt and wind down window.

o Use low range 2nd gear (in most situations).

o Drive at a steady speed to create a bow wave.

o Avoid using the clutch.

o Do not over-rev engine if you lose traction.

o If engine stalls, place in neutral without using clutch to restart. Takeoff in 1st low.

· Post Water crossing maintenance

o Check diffs etc for water if depth above axles.

Check winches if fitted.

It is usually best to tackle a hill climb that’s any sort of challenge in low range. Although you may be able to just reach the top of a hill climb in 1st high, it doesn't leave you with any lower gears if the need arises. By using say 2nd or 3rd low range instead of 1st high, you have lower gears available if needed. If you run out of gears on a hill climb, you may have to back down to the bottom of the hill and start again. Most 5-speed gearboxes allow vehicles to travel up to 6Okm/h in low range, so you don't have to be continually swapping between low and high range as you travel between hills.

Diesel vehicles are generally better for hill ascents and descents as they usually have better low rpm torque for climbing the hill and higher engine compression for descending. However, in long sandy hill ascents, where traction is low and a run-up is required, the greater power of gas engines can be an advantage.

When descending hills, you should always be in low range and have selected the gear required before descending. You should always avoid braking on downhill sections as you run the risk of locking up your wheels, causing a slide. Engine braking slows the vehicle without causing wheel lockup. However it is better to use the brakes than allow the vehicle to 'run away' and pick up speed. Always apply the brakes gently, rather than applying them abruptly and risking a wheel lockup.

Often hills get steeper the further you go down, so its best to be in 1st low from the beginning rather than having to try and change gear halfway down. When changing down a gear while descending, it is best to be feathering the brakes as you depress the clutch, as otherwise the vehicle freewheels while the clutch is depressed and picks up speed. It is far better to be in too low a gear and travel down slowly rather than be in too high a gear and have a potentially dangerous situation arise.

Hill Stall Recovery

A very common occurrence on hill climbs is the stalling of the vehicle when the hill becomes too steep. When this occurs, you will be left in gear with the engine switched on but stalled. To recover from this situation you should perform a Hill Stall Recovery, rather than just fire up the engine. This is accomplished by:

· Switch the (stalled) engine off and place your foot firmly on the brake.

· Depress the clutch and select reverse gear in low range.

· Take your foot off the clutch then slowly take your foot off the brake. The vehicle is now in reverse gear with the stalled engine stopping it from rolling down the hill.

· After checking the track behind is clear, start the engine and keep your feet off all pedals.

· The starter motor will start to drive the vehicle backwards as the engine begins to fire.

· This will result in a smooth downhill progression while starting the engine and ensuring you have been in gear at all times. If you simply start the engine and then select reverse gear, it will result in a fast jerky takeoff and being out of gear during some stage of the takeoff.

The Hill Stall Recovery does not apply to automatic vehicles as they should never stall, just lose forward drive when the hill becomes too steep for the gear its in. When this occurs, simply place your foot on the brake while restarting the engine, select the appropriate gear and gently take your foot off the brake.

A lesser used method after an uphill stall can be done in situations where the terrain is not extremely steep and you wish to continue forward up the hill but you do not wish to attempt to let the clutch out while trying due to tire spin. This method only applies to manual transmissions and drive trains that have very low forward gears. By leaving the vehicle in gear and starting the engine without pressing the clutch in the vehicle will begin to move forward while the engine fires. Once the engine fires you can begin forward movement. This method is hard on the starter and electrical system and should not be attempted on very steep terrain due to the possible overload on the electrical system and starter. Some vehicles will not allow the starter to be engaged if the vehicle's clutch is not depressed. In some cases this feature can be overridden by use of a clutch safety cancel switch.