AWD vs. 4WD

[Mr.Samples]

could someone explain the diff between AWD & 4WD or are they the same thing

 

[Antilles]

the very basic explanation:

AWD turns all 4 wheels all of the time. 4WD turns two of the wheels until they slip, and most often can be manually switched between 4WD and 2WD.

 

[Defiant]

Eh, it's mostly semantics, though many have tried:

http://www.difflock.com/offroad/4x4explained.shtml

Definitions

It is important to get the definitions down first, since for any four wheeled vehicle, all wheel drive and four wheel drive literally mean the same thing. Generally speaking "all wheel drive" implies permanently engaged or automatically engaging four wheel drive and "four wheel drive" implies manually engaging, part time four wheel drive. The auto industry usually abide by these definitions but not in all cases.

Pretty good site, four times the information you'll ever need, but nice to read at work....

 

[TheSh111t]

In a 4 wheel drive system, the front differential is forced to spin at exactly the same speed as the rear. There is a direct link (Chain or gear) between the front and rear. Not a problem when you are driving off road where the wheels can slip or your driving in a strait line, but when you make a turn, especially a sharp turn (Parking or U turn for example) the front wheels are moving along a larger arc then the rear so you run into binding and often chirping of the tires. This is why you are not supposed to engage 4 wheel drive on the street.
All wheel drive however links the front and rear differintials with a viscous coupling or a torsen (SP?) type unit. So the front and rear differentials can move at SLIGHTLY differant speeds. So when you are turning into a parking stall or whatever and the front wheels travle on a bigger acr as opposed the the rear, like I spoke of earlier, the front wheels are allowed to travle slightly faster then the rear (There is a little give) this eliminates the binding and churping you can experiance in a 4 wheel drive system.
For hard core off roading true 4 wheel drive is better. (Gears do not slip, you get equal power to bot front and rear differnetials wthought the slippage that is encountered in an all wheel drive system) But you can not engage 4 wheel drive on the street, so you are esentually carrying all that weight around for nothing. For onroad sure footedness all wheel drive is the only way to go.