what is the difference between 4wheel drive and all wheel drive??

Answer 1

Four wheel drive, is a system that powers all four wheels at all times and can be used full time on all surfaces including pavement. The additional feature of a differential incorporated into the transfer case makes it possible to use 4WD all the time. Each tire creates about 25% of the available torque when the ground is level with a consistant surface. Driver has a choice of a "4-high" (that's your every day setting) and "4-low".

When "4-low" is selected the wheels create substantially more torque (on a Grand Cherokee its 2.72 times more) than in "4-high" - at the same time the vehicle moves at substantially slower speeds (2.72 times slower on a Jeep Grand Cherokee).

Important: "4-low" does not create more traction - it creates more torque and that can be detrimental when traction is marginal. Slipping tires are more likely in "low" than in "high"!

The low setting is an advantage for drivers who need to tow and maneuver a heavy trailer etc. and for drivers who at one point or another may want to negotiate difficult off-road terrain, when more torque and/or slower speed is needed.

All wheel drive (AWD) is a system that powers all four wheels of a vehicle at all times as well. Full time symmetric AWD would be the best term to be used. Difference to full time 4WD is that a "4-low" setting is not available in AWD cars. Due to the lack of "low range" AWD vehicles are much less capable in off-road settings than full time 4WD vehicles, but work perfectly well on-road.

Here is how it works: During traction loss at the driven axle (could be front or rear) a fully automatic system (hydraulic, mechanical or electronic) routes torque to the axle with traction. This means you have to completely lose traction in 2WD on your driven axle first and then the other axle will take over and try to keep the car moving and stable. So, for a moment you have AWD. Once the primary driven axle regains traction and both axles rotate at the same speed again, the system reverts back to 2WD.

Answer 2

The terms are not always used correctly

http://en.wikipedia.org/wiki/Four-wheel_drive

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According to the article, AWD is a vehicle that is always in 4 wheel drive mode. And 4 wheel drive can be switched between 2 wheel drive (mostly front wheel drive) and 4 wheel drive (for low traction drive - like snow and mud). In fact these vehicle MUST be switch because the 4 wheel drive mode is only for low speed / low traction mode.

I have an Audi quatro (AWD) and I have to say AWD is probably the best for most people. There are time that they are so maintenance free that I've forgotten I have a AWD (meaning that I thought I would be stuck in the snow when it would be fine).

Answer 3

Foru wheel drive is when you set it
All wheel drive is a system that takes over when it feels you are going to be in snow or more rugged terrain.
Frankly, I've had four wheel drives and one all wheel drive.
I prefer the four wheel drive as you can control your driving.
The all wheel was probably put in cars as the people did not know how to operate four wheel and blew out the tranmissions on the cars.

Answer 4

How they get the wheels to turn. AWD uses some sort of torque convertor (?) or electronic control to engage all 4 wheels, and 4wd has direct mechanical link that permanently drives all four wheels. A lot of AWD are 2wd until the computer or torque converter notices slip and then applies awd. In the early days, before computer control, you could get an awd stuck in the sand as all wheels felt slipping and tried to transfer power to the wheels with grip !

Answer 5

4 wheel drive you have the option of changing between 4 wheel,or 2 wheel drive. all wheel drive is constantly driving all 4 wheels at one time. you can never change to 2 wheel drive

Answer 6

Nothing much but a four wheel drive you can chose two wheel drive or four wheel drive.

Answer 7

Some trucks, especially army trucks, have three axels - - all of them under power. In the Second World War in Europe. I was in the anti-tank. Three of my trucks were 6X6 (all wheel drive) and my command car, a jeep was 4X4.