What are the differences between all-wheel-drive (AWD) and 4-wheel-drive (4WD)? These systems are very common on many cars, trucks, and UTVs these days. The two acronyms are often used interchangeably and the differences aren’t crystal clear. The confusion partly arises from automotive manufacturers describing their systems in their own specialized way.
TFL 101 is our new video series that gets to bottom of automotive question. We do not just sit there – trying to explain it. We actually go out and demonstrate how something works and what the differences are.
On this episode (Ep.1), Roman and Tommy take a new VW Alltrack with a sophisticated AWD system and an old Jeep Cherokee with an old-school 4WD (or 4×4) system up Gold Mine Hill off-road trail.
Both, the 4WD and AWD accomplish a similar task. They provide engine power to all four wheels, but they do so in very different ways. Here is the difference. A four-wheel-drive system makes use of a selectable transfer case with a low gear range. A low range gearbox affects the ratio between the engine speed and the wheel speed. Effectively, a low-range transfer case increases torque at the wheels at a low speeds, allowing for more precision and control in difficult off-road situations.
Tommy’s Cherokee has an old-school 4×4 system with a low-range gearbox that multiplies available engine torque at a ratio of 2.72 to 1. It’s like riding a bicycle. When you use a lower gear, it’s easier to pedal – but you are moving slower. When you use a higher gear, you can go faster, but it is harder to pedal. Rock crawling does not need high speed, so the control and precision of a low range comes in handy.
A trasferì case found in a typical truck or four-wheel-drive SUV has different settings to send power where needed. For regular day-to-day driving the power is sent to the rear wheels in 2WD mode. When the surface gets slippery, the transfer case can be manually switched into 4×4 “high” mode. Now the power is divided and sent to the front and rear axles. When the terrain gets steep and rocky, 4×4 “low” mode can be selected after the vehicles comes to a stop and the transmission is in neutral.
The all-wheel-drive system in the VW Alltrack can also send power to front and rear axles, but it does not have the extra off-road capability of the low-range transfer case. Volkswagen’s AWD system is called 4Motion. It uses a haled coupling which allows different amounts of power to be sent to the front or the rear. The system uses wheel speed and other sensors to determine how much and when to allocate the power to each axle. During regular driving, about 90% of power goes to the front wheels, and 10% goes to the rear. 4Motion is capable of changing the power distribution ratio in an instant if it detects loss of traction at one of the wheels.
There is also a traction control system that brakes the wheel(s) that do not have traction. It forces the power to wheel(s) that are in contact with the road and have traction.
Watch the video for the demonstration.