Four-wheel-drive use in Industry and Government is all about being safe and productive whilst on the job and there are a few simple things you can do to help that cause. The vehicles you are using have a unique set of features to make them more mobile and it makes sense to fully explore the vehicle’s true potential on that fieldtrip you are about to undertake, so here are a couple of ways to get you started.

Understanding 4WD – Part-Time 4WD (as seen on Hilux and Land Cruiser 79)

Both Hilux and the 79 series Land Cruiser use a basic part-time 4WD system. In its purest definition it is a form of 4WD that can be engaged on any loose surface and should be used ANY TIME you depart a bitumen road. It won’t however sustain use on a hard surface, like bitumen, concrete or paving, as transmission damage can occur.

You have three choices – 2H (two-wheel-drive HIGH range) for bitumen roads and other hard surfaces, 4H (four-wheel-drive HIGH range) for high-speed dirt roads/hard packed clay swales/firmer coastal and desert sands where speeds in excess of 50km/h are sustainable/desirable, 4L (four-wheel-drive LOW range) for low-speed <50km/h steep or boggy terrain where finesse is required over difficult terrain.

In both vehicles’ cases, the engagement of the HIGH range modes can be done on the move and at speeds up to 100km/h (not that I’m encouraging you to do that because 80km/h is a much safer maximum speed on dirt). Moving between 2H>4H>2H is preferably done in motion, no need to stop.

LOW range is a different proposition though. As it is a slow-speed gear set you’ll need to come to a complete halt before you select LOW range and if you are driving an automatic transmission vehicle, select N (neutral) with the main gear selector. Left in D (Drive), R (Reverse), P (Park) will result in a malfunction – typically a warning indicator flashing, an audible alarm or a horrible gnashing of gears sound that can’t be good for the gearbox!

In the case of the Hilux the procedure for 4WD operation is this…

• Driving down a bitumen road (at posted speeds) you observe the bitumen terminates and dirt continues
• As you approach the surface change, get off the accelerator pedal (this takes load off the transmission and facilitates easier engagement of 4WD) and start the slow-down process (assuming you were doing 100-110km/h)
• Roll onto the dirt with the steering wheel in the dead-ahead position (ensures front and rear wheel speeds are synchronised)
• Reach across to the 4WD selector (that rotary dial adjacent to the heater/AC controls) and switch it from 2H>4H, and within the space of a car length’s-worth of travel, you’ll see a green 4WD indicator light aglow on the dashboard, telling you that the front differential has been activated and now we have all four wheels driving the vehicle down the road – that’s good!
• Automatic or Manual transmission variants behave exactly the same, no need for a clutch dip with the manual either!
• Use of 4H on dirt is to be encouraged because 1) you’ve got the facility there and it’s free, so use it, 2) you’ll be safer, 3) along with sharper steering also comes shorter stopping distances and less wear and tear on tyres (the accountants will like that). It is also a widespread Industry practice, especially in Mining, where a dramatic reduction in casualty crashes has occurred since its policy adoption twenty-plus years ago. It should be your policy too!
• If the road deteriorates and it now resembles a goat track, full of ruts, boulders, boggy bits or suddenly steep, then STOP!
• Dial-up LOW range 4L on the selector (in an automatic with the main gear lever in N (Neutral)), (in a manual with the clutch dipped) and watch the corresponding dashboard symbol confirm success
• With LOW range engaged, grab your preferred gear and off you go, albeit at a much slower pace but with a multiplication of torque which is good for dealing with softer surfaces that would ordinarily sap the vehicle’s power and potentially contribute to a bogging
• WARNING – use of 4WD on a hard surface (bitumen/concrete/paving) will likely result in a phenomenon called “wind-up”, where conflicting wheel speeds between front and back and left and right, twist the driveline up and bind, putting loads on components that can and do break (the accountants won’t like that).
• If you failed to disconnect the 4WD system on those hard surfaces you’ll likely notice after turning a few corners that the vehicle feels like you’ve left the handbrake on, it might skip around a corner or you might hear gear sounds you are unaccustomed to. They are all hallmarks of wind-up.
• To relieve it you will benefit in having a loose surface under the wheels and possibly reversing the vehicle as you deselect 4WD. A flashing 4WD light will be telling you that there is still some pent-up tension in the driveline and needing relief  

In the case of the Land Cruiser 79 Series the procedure for 4WD operation is this…

• Prior to your journey you need to ask yourself whether you will be driving on a dirt road that day? If the answer is yes, get the wheel brace from the tool roll packet and spin the centre hex-nut seen in the front wheel hub assembly from AUTO to LOCK. This fixes the front wheel/hub assembly to the front axle more reliably than the AUTO position and with no likelihood of breakage because the AUTO position is brittle
• Driving down a bitumen road (at posted speeds) you observe the bitumen terminates and dirt continues
• As you approach the surface change, get off the accelerator pedal (this takes load off the transmission and facilitates easier engagement of 4WD) and start the slow-down process (assuming you were doing 100-110km/h)
• Roll onto the dirt with the steering wheel in the dead-ahead position (ensures front and rear wheels speeds are synchronised)
• Reach down to the 4WD transfer lever (adjacent to the main gear selector) and pull it back from 2H>4H, and within the space of a car length’s-worth of travel you’ll see a green 4WD indicator light aglow on the dashboard, telling you that the front propellor/driveshaft has been activated and now we have all four wheels driving the vehicle down the road – that’s good!
• Being a manual transmission in this vehicle variant, no need for a clutch dip!
• Use of 4H on dirt is to be encouraged because 1) you’ve got the facility there and it’s free, so use it, 2) you’ll be safer, 3) along with sharper steering also comes shorter stopping distances and less wear and tear on tyres (the accountants will like that). It is also a widespread Industry practice, especially in Mining, where a dramatic reduction in casualty crashes has occurred since its policy adoption twenty-plus years ago. It should be your policy too!
• If the road deteriorates and it now resembles a goat track, full of ruts, boulders, boggy bits or suddenly steep, then STOP!
• Select LOW range with the transfer lever by lifting the lever a little before pulling it back. Sometimes that action can be an utter-bastard, especially on new vehicles, so a profanity or two is permitted! No clutch dip required
• With LOW range successfully engaged, grab your preferred gear and off you go, albeit at a much slower pace but with a multiplication of torque which is good for dealing with softer surfaces that would ordinarily sap the vehicle’s power and potentially contribute to a bogging
• WARNING – use of 4WD on a hard surface (bitumen/concrete/paving) will likely result in a phenomenon called “wind-up” where conflicting wheel speeds between front and back and left and right, twist the driveline up and bind, putting loads on driveline components that can and do break (the accountants won’t like that).
• If you failed to disconnect the 4WD system on those hard surfaces you’ll likely notice after turning a few corners that the vehicle feels like you’ve left the handbrake on, it might skip around a corner or you might hear gear sounds you’re unaccustomed to. In the case of the Land Cruiser 79 you might also notice the transfer lever is stuck and won’t budge. They are all hallmarks of wind-up.
• To relieve it you will benefit in having a loose surface under the wheels and possibly reversing the vehicle as you deselect 4WD. A 4WD light still aglow will be telling you that there is still some pent-up tension in the driveline and needing relief. Going in reverse will un-wind the transmission and free up the transfer lever for disengagement

Effective Tyre Management

Now that you are full bottle on 4WD operation, it is time to turn our attention to the second-most thoroughly confused subject when it comes to 4WD use and that is tyres and tyre pressure!

Motor vehicle manufacturers know that around 90% of their 4WD vehicle sales go to owners who have no intention of going bush, they are stuck in the city, so most new vehicle sales come with Passenger (P) car tyres fitted as standard. These are a compromise, trying to perform too many purposes and excelling at none – offer a comfortable ride around town, have an adequate ability on perfect or less perfect surfaces and carry a load with plenty of resilience. They fail on most counts.

If you are reading this, it is because you are operating a 4WD in a commercial environment and therefore you’ll need something better.

In a nutshell, that will be a Light Truck (LT) tyre and running an all-terrain (A/T) tread face, the great all-rounder!

With that selection will come these significant benefits – a deeper 13mm tread depth (Vs 9mm), a tougher tyre carcass, better able to carry a load and withstand punctures and a tyre that steers and stops on all surfaces better. The accountants will also like that they last longer, but only if you get involved in a pressure regime that can make you failure-proof.

Selecting that A/T tyre also needs a little scrutiny, in particular examining the data stamped on the sidewall.

A standard Hilux tyre will say something like this…

• 265/65R17 112S – 265mm wide, 65 aspect-ratio (fancy way of saying 65% of the tread width amounts to the sidewall height), R = Radial construction, 17 = 17” diameter wheel, and the important number 112 = 1,120kgs carrying capacity stated as the Load Index (LI), whilst S = 180km/h the Speed Rating

What you really need is this…

• LT265/65R17 120R – same initial information with the exception of the LT reference = 13mm tread depth and heavier construction, but the bigger news is the 120 load-index = 1,400kgs, whilst R = 170km/h

Your Land Cruiser 79 series might quote this…

• 265/70R16 115R – 265mm wide, taller 70 sidewall and fitted to a 16” wheel, 115 = 1,215kgs

What you will want is this…

• LT265/75R16 123R – same initial information with the exception of the LT reference = 13mm tread depth and heavier construction, the taller 75 sidewall, but the bigger news is the 123 load-index = 1,550kgs

Using a tyre with a minimum 120 load index is the threshold I know that works in ensuring a long-life with minimum pain and we call it the 120 Rule. Demand it of your tyre vendor so you get a 120 load-index (or greater) and in LT construction. It will save you a lot of pain and again the accountants will love it, because you won’t suffer tyre failures ever again (with careful pressure management)!

Now that you have the right rubber, let us consider the pressures.

Toyota have thought long and hard about that advice and they offer it up via a decal affixed to the vehicle by the driver’s door and called the Tyre Placard.

Now, whilst the placard was conceived with a mindset of using the standard rubber that came with the vehicle, it still has relevance, even with an alternative LT A/T fitment.

You see, the whole tyre pressure equation revolves around three factors – pressure/load/speed.

• As you add weight to a vehicle, the pressures need to go up to support the increased weight
• If you travel at high speed on the highway, you’ll need increased pressure (per the placard recommendation) to regulate the temperature of the tyre
• Remove load (when empty) or slow down (when off-road), you don’t need as much air

The placard on a Hilux and running 17” wheels offer a couple of pressure settings, which, from my experience work (provided you are not going ridiculously oversized), whether you are running P or LT tyres and depending on your weight.

When empty (unladen with 2 occupants and 400kgs of luggage or less) both front and rear need only 200kPa = 29psi. On my vehicles I round that up to an even 210kPa = 30psi, it is easier to remember and in their local use and carrying little gear 210kPa/30psi gets me a tyre that is comfortable and lasts for an extraordinary life. I expect anywhere between 80-90,000kms travelled and still with tread left on the tyre before I replace them.

When heavy and approaching the vehicle’s GVM (Gross Vehicle Mass) the placard pressure bumps a bit, 230kPa = 33psi for the front and 250kPa = 36psi for the rears. Even with a heavy load, those pressures will preserve a modicum of comfort and steer and stop appropriately.

There will likely be co-workers and others who are dissenters on this point and will recommend to you starting pressures of 280kPa/40psi or more as being more relevant. What they fail to recognise is that those pressures are designed to carry far greater loads than Hilux will ever impose on its axle pairings and are unecessary, gifting you a much rougher ride, more punctures and prematurely worn out tyres. Not desirable!

The placard on the Land Cruiser 79 series and running the 16” wheel variant (265/70R16 115R) from earlier in this discussion offers this info from the placard and again it’s right.

When empty, 250kPa = 36psi front and rear works and when fully laden and approaching GVM, 350kPa = 51psi for the rears only, is what is needed.

These pressures for Hilux and Land Cruiser 79 are what are required when on the bitumen and using the stated sizes and at the assumed loads the vehicles were designed for, further refinement is required for dirt roads and later off-road. The danger with overinflation, and I see this all the time, are tyres worn out before their time, greater puncture susceptibility, nervous steering, a rough ride and extended braking distances, none of which is desirable.

The off-road pressures are a whole other chapter, so we’ll leave that alone for now, but what I will share with you is this super-useful setting if you are going to be driving on a dirt road all day. We call it the 20% Rule and meaning, when you leave the bitumen behind and intend clocking up some kays on the dirt that day, drop your pressures from the placarded levels by 20% and slow down by 20%, no faster than 80km/h.

Reducing the pressures introduces some flexibility in the tyres and they then can cope with rock impacts and likely survive the big hits, especially since you slowed down as well. I intensely dislike having to do field changes of tyres through negligent failure and luckily for me, I haven’t lost a tyre in the bush or on a trip in 25 years, thanks largely to this pressure regime. You too can make yourself puncture-proof with the right tyres and the right pressure application!