It’s what makes your 4WD a 4WD…
Your rig’s transfer case is what makes it well, a proper fourby. It’s a specialised component that’s fitted on all 4WD and AWD vehicles.
There are various types of transfer cases used in different vehicles, but the essential function is to ‘transfer’ power from the engine, through the drivetrain to the wheels, via the front and rear axles.
4WD vehicles will have either a full time or part time transfer case. Depending on the type, either chains, hydraulics or gears are used to aid in the distribution of power.
FULL TIME 4WD
Many specialised offroad vehicles like Toyota’s 200 Series LandCruiser, the 70 Series LandCruiser range and the 150 Series Prado are equipped with fulltime 4WD transfer cases.
In these vehicles, the transfer case is always sending power to both the front and rear axles.
Older full time 4WD were known for being less fuel efficient, and while this is still the case to an extent, the slicker modern systems have righted plenty of wrongs.
In order to maximise traction and ensure an even distribution of power between both axles when driving full time 4WD vehicles offroad, you’ll either need to shift the vehicle into low range 4WD mode, or in some vehicles utilise a differential lock button.
PART TIME 4WD
Part time 4WD systems are utilised in plenty of modern SUV vehicles like the Isuzu M-UX, as well as a majority of offroad utes like the Toyota HiLux and Isuzu D-MAX.
The transfer cases utilised in part time 4WD vehicles allows the option of sending power solely to the rear wheels via the rear axle when driving around town, on the highway and in light offroad settings.
Shifting the vehicle into high range 4WD (4 Hi), engages both axles and evenly distributes the engine’s power between both axles.
The 4WD low range setting (4-Lo) can also be engaged in order to access further torque and achieve more traction when tackling rough or slippery terrain offroad.
AWD or All Wheel Drive systems are common in plenty of modern light SUV vehicles including Suburu Outbacks and Foresters.
While not ‘proper’ 4WDs, an AWD equipped vehicle does in fact utilise a transfer case in order to distribute power to both of the vehicle’s axles and all four wheels, as the name implies.
In vehicles with symmetrical AWD systems, both axles receive power constantly and if the vehicle starts to lose traction, more power is delivered to the axle that needs it.
On-demand AWD systems work differently. All power is delivered to the vehicle’s front axle under normal onroad conditions, however if the vehicle starts to lose traction, power is delivered to the rear axle for stability.
AWD vehicles are able to receive power to both front and rear axles, but both axles must be able to rotate at different speeds, whereas the transfer cases fitted in legit 4WD vehicles force both axles to spin at the same speed.