Written in 2015
There are many varied vehicles on the market today. All are good vehicles for their intended purpose. It is the choice of vehicle for the purpose intended, which will determine if your vehicle is the correct one for you. Choose carefully, there is no point in having a designated ‘rock crawling’ vehicle to drive to work and back or if you aim to have three children and a dog along on your off road trip.
However, if this ‘rock crawler’ is your weekend toy then it may be the right choice of vehicle for you.
Most people have to compromise, as to the type of vehicle that they choose to purchase. The vehicle normally has to fulfill a number of roles in our ever-crowded lifestyle. Some examples, of this may include a weekly work vehicle, or a ‘mom’s taxi’ for the school run.
Most, vehicles can be safely confined to a few categories.
- Commercial type vehicles, both single cab, x-tra cab, or dual cab layouts.
- Wagon (SUV) type vehicles and ‘soft-roaders’
Commercial Type Vehicles
Predominately with very few exceptions they have a ‘part-time’ or selectable 4WD layout. With very few exceptions, they all have a leaf spring layout for the rear, that aids in their load carrying ability. Most commercial vehicles also have a braking system, which has a disc front and a drum rear setup. Commercial vehicles have a full chassis, normally referred to as a ‘ladder frame’ chassis.
These vehicles are usually derived from commercial vehicles and have evolved to include fully enclosed bodies. They either a five seat or more layout. Some wagons have coil spring rear suspension, which aids in passenger comfort at the expense of the load carrying ability. Wagons, also have either a combination of disc brakes all round, or disc/drum setup similar to their commercial siblings. The chassis comprises of a mixture of traditional ladder style chassis layout or a monocoque construction. Wagons can have either part time or full time four-wheel drive systems
Monocoque Construction Explained
Monocoque construction is a term used to describe the way the vehicle is constructed. This means that the body of the vehicle has the components of the suspension attached directly to it. There are advantages and disadvantages to this type of construction process. Generally, the vehicles are lighter, due to the fact, that they do not have the additional weight of a chassis. Monocoque constructions has the added benefit of engineering safety features. These features enabled vehicle engineers to allow various types of material as well as different thicknesses of material to be constructed in such as way, as to allow the properties of the material, metal, to deform and thus absorb energy in the event of an impact. The structural rigidity of the vehicles can also be increased, allowing the vehicle to be stronger and lighter than traditional chassis type vehicles.
Full chassis vehicles were traditionally manufactured, due to the ability of the manufacturers to fit various body styles and configurations to a similar chassis.
This reduced costs and also allowed for easier repairs. Traditional chassis vehicles are generally referred to as ladder frame chassis. The construction of the chassis resembles a ladder. Two long chassis rails are joined together with various cross members, which resemble the ‘rungs’ of a ladder. Generally full chassis vehicles are heavier as the body has to be bolted to the chassis. It is easier to eliminate Noise, Vibration and Harshness (NVH) in a traditional chassis type vehicle by insulating the body from the chassis. Rubber spacers or blocks are used to achieve this.
Part Time Four Wheel Drive Systems, allow the driver to select between Two Wheel Drive, (generally the rear wheels) and Four Wheel Drive. Automatic locking hubs or manually selected ‘Free Wheeling ‘hubs achieve this.
Full Time Four Wheel Drive is achieved through a combination of differentials. This type of drive arrangement is usually associated with a ‘center diff lock’, which can be automatically engaged or can be manually selected by the driver.
Soft Roaders can consist of a wagon style or sedan/hatchback style layout and can also comprise suspension and braking systems similar to the wagons. It would be rare to find a soft roader that did not have a monocoque construction for the body. Most soft roaders have an ‘on demand’ four-wheel drive system. Some have the ability to lock the drive train to allow a moderate degree of power to be transferred to all four wheels.
Soft Roaders with ‘On Demand Four Wheel Drive’ systems generally do not have a low range transfer gearbox. They are usually front wheel drive, until such time as a certain degree of slippage is detected in the front wheel drive system, whereby the rear wheels can then be progressively added to the drive line. Some Soft Readers also allow the center diff to be locked, thereby ensuring that there is a constant supply of drive to the rear wheels.
Take the time to understand the various gearbox ratios, not only gear selection. Try Low range as well as High Range and feel the difference that this makes to the way the vehicle performs. Many people become confused as to when to place their vehicle into ‘Four Wheel Drive’ either by selecting the lever, rotary dial or button to change from two-wheel drive to four-wheel drive, in part time four wheel drives. In full time or permanent four-wheel drive vehicles, you may still be required to manually select the lever, or press a button, to lock the ‘center differential’.
It is advisable to select four-wheel drive the moment you leave a bitumen surface. Vehicle stability and safety is greatly enhanced, when four wheel drive is selected, as the vehicle now has the front wheels pulling as well as the rear wheels pushing, thereby allowing the vehicle to become more stable in the event of an emergency maneuver occurring. Tyre wear and damage to the road or track surface will also be minimized by selecting four wheel drive early.
Most modern vehicles allow the selection from two-wheel drive to four-wheel drive to be undertaken whilst the vehicle is in motion. Due to the fact that most modern vehicles now have automatic ‘free wheeling hubs’ in the front axle, we are not required to stop to lock these ‘free wheeling hubs’ into the locked position. Some vehicles such as the Land Cruiser 70 series range, still have ‘free wheeling hubs’ which when engaged for the first time, will need to be locked when the vehicle is stationery. Thereafter, the vehicle can be transferred from 2H (two-wheel drive) to 4H (four-wheel drive, high range) whilst the vehicle is moving.
Transferring a vehicle from 4H (four-wheel drive, high range) to 4L (four-wheel drive, low range) must be undertaken when the vehicle is stationery. Some manufacturers allow this to occur at limited speeds, however if you are unsure if your particular vehicle has this capability, then bring the vehicle to a complete stop. Likewise, some drivers can change from 4L to 4H, through a practiced sequence utilizing ‘double de-clutching ‘ techniques which are not for the novice driver.