Many times we talked about AWD and 4WD,what they are and what they really mean? Let's see:
If you do a lot of driving, odds are, you've been in some situation where your wheels have started to slip, and maybe you got stuck or your car started to slide. While, drive wheels are connected by an open differential will lead all of the power go to the slipping wheel. The wheel with traction won't spin at all, which leaves you stuck, or unable to recover from your slide.
Most cars only send power to two wheels, either at the front (in front wheel drive or FWD) or the rear (in rear wheel drive or RWD). To deal with the kind of traction-loss situations described above, automakers developed four wheel drive (4WD) and All Wheel Drive (AWD) systems.
Yes, there is no big difference. Just each automaker call by their own system. Which really matters is do they have part time 4WD or full time 4WD.
For part time 4WD,which used in many pickup and SUVs. When 4WD is engaged, the front and rear wheels are locked together and spin at the same speed. That's the strength and the weakness of this system. In slippery situations, it keeps all the wheels working. It's not very good on dry pavement and can make cornering difficult, though. Besides Since the front and rear wheels are locked together in 4WD, things can bind up while turning which can lead to a sort of herky-jerky, hopping motion.
Engineers wanted a way to get the benefits of part-time full wheel drive, but without the need for driver input, so they developed full-time 4WD. These systems have more or less the same layout as part-time 4WD with the addition of a differential. The differential allows the driveshafts to rotate at different speeds and makes cornering smoother.
The AWD systems used by Audi and Subaru are a further advancement from full-time AWD. These systems do not have a front driveshaft. Instead, the front wheels are driven by a transaxle. Essentially the transmission also contains the front differential. The front differential also connects to a limited slip differential that sends power to the rear wheels. This called the center differential.
Under normal driving conditions, power is evenly distributed to all four wheels. The center differential allows the front and rear wheels to spin at different speeds for proper cornering. If there is significant slippage between the two sets of wheels, though, the limited slip center differential will send power to the other wheels.
So ,next time when they talked about their 4WD or AWD vehicles, you can easily know their Pros and Cons.
