4WD vehicles are designed to drive through obstacles that conventional (2WD) vehicles would not be able to overcome. Many places in the New Zealand bush are simply not negotiable without a 4WD however simply owning such a vehicle does not mean that you can drive it safely.
Driving a 4WD vehicle requires a fair degree of understanding about the mechanics of the transmission and the effects that water and dust (common occurrences on off-road tracks) may have upon your safe progress. Every owner of a 4WD vehicle should check these essential skills and practice them before going off-road.
The skill in tackling rocky conditions is to keep the tyres pointed to the high ground at all times. This avoids “high centering” (hanging the vehicle up on diffs, the transmission or bashplates). Torque is more important than power in climbing rocky slopes, so select first or second gear low range to ease the vehicle over any obstacles. Use minimal throttle to prevent tyre slip. Where possible, stick to recommended road tyre pressures, only dropping them when the vehicle is stuck and all other recovery techniques have failed. Though lower pressures maximise the tyre footprint, they also increase the danger of pinching the tyre in a narrow crevice or slashing the sidewall on a tree stake
The most common “mud negotiation” confronted by the average four-wheel driver is a boghole on a bush track; usually furrowed with massive wheel ruts and axle-deep pits. Where possible, place the tyres on high ground to avoid dragging the diffs through the mud, but if you slip off, keep the accelerator down and turn the steering wheel from side to side, enabling the side lugs of the tyres to gain purchase on the side face of the ruts. Check for build up of mud in the guards. Clogged guards effectively eliminate any tread pattern on the tyres, so clean them out with a shovel where necessary. Getting through mud requires momentum, so as a general rule, high range and a steady throttle are recommended.
On the beach
Where possible, stay in high range four wheel drive to maintain speed, but if you bog down, go into low range and try again. Everything depends on the conditions. Driving on coarse, hardpacked sand can be like rolling along a super highway, but more often, beaches will be windblown, with soft and traction-sapping sand, requiring continual momentum, full throttle and partially deflated tyres. Absolute minimum pressure 102 – 110 kPa. Dropping pressure “bags” the tyre, creating better floatation through a wider footprint. Re-inflate as soon as possible after leaving the beach. En route to the service station drive at a maximum of 80km/h.