AWD vs. 4WD

[gfreek]

Whats the difference between AWD and 4WD???

[RningOnFumes]

all wheel drive can be found in a lot of cars---- basically all four wheels drive ----it's on all the time

4x4 is on the vehicle, but is not on all the time...and there are different settings depending on the difulculty of the terrann


in other words---on is for the road, the other is for the dirt...----grossly simplified

[gfreek]

Ok, the Matrix is 4WD, all 4 wheels are pulling the same?? I understand the 4WD you have to engage,like on a Pick UP or SUV however it's kinda confusing between that, what the Matrix has, and AWD. If the right front wheel on the Matrix slips, does the left front engage or if both front wheels slip, does it give more power to the rear or if the rears slips????

[greywolf]

The Matrix has a viscous coupling at the rear axle that is connected to the drive shaft from the engine. It's like a bunch of clutch plates in a thick liquid. Every other plate is connected to a different end of the drive system. If the wheels at both ends are traveling at the same rate as in typical dry pavement travel. Pretty much nothing is happening back there because all the plates are moving at the same rate. If a front wheel slips, it moves faster than the rear wheels causing the plates attached to the front drive to start transfering power through the fluid to the plates in the rear drive.

Honda uses pretty much the same system in the CRV which they call an AWD system. Toyota's 4WD badge on the car looks more like an A than a 4 because whether a car is marketed as 4WD or AWD seems mostly a marketing decision. Cars marketed as AWD in the U.S. are often marketed as 4WD overseas.

4WD in the U.S. usually means the vehicle is normally running 2WD, a driver's input is required to select 4WD, the connection is hard rather than viscous, and it has greater ground clearance. Additionally, a lower gear range is normally selectable for difficult terrain. The Matrix has none of those qualities. 4WD most often means a vehicle is meant to handle off road situations while AWD is meant for on road situations in difficult conditions like snow on pavement or rain on a dirt road.

While the Matrix is marketed as 4WD, its system is typically called AWD by other manufacturers. I have no intention of taking mine off road.

[Salsa03]

This can also help explain and understand the advantages of both 4WD and AWD

Park the Jeep Liberty and Saturn Vue sport utility
vehicles side by side, and stand back 50 feet, and
obvious differences are minor. Get closer, and look
deep, and the differences become major.

Those differences are not so much specific to those
two vehicles, but to the design philosophy behind
them. One, the Jeep, is a member of the
truck-based group of sport utes, which also includes
the Nissan Xterra, Ford Explorer, Chevrolet
Trailblazer, Toyota Sequoia and Dodge Durango.

The Saturn belongs to the car-based SUV club.
Others include the Toyota Rav4, Honda CR-V,
Subaru Forester, Toyota Highlander and Lexus
RX300.

Is one kind better than the other? Yes. But it
depends on what you are looking for. And if you let
the manufacturers tell you what you are looking for,
it can get confusing.

Honda, for instance, has no real truck-based SUVs,
because they have no trucks on which to base their
sport utes. And while the Honda CR-V and Pilot
are excellent SUVs, they are not as adept at rugged
off-road duty as some of their truck-based
competitors. However, their on-pavement manners
are impeccable, because they are, after all, based on
car platforms.

Nissan's sport utes are truck-based. A Nissan
Xterra costs about what a Honda CR-V costs, but
the Xterra is considerably more at home in the
woods. But the Xterra has a rougher ride around
town -- not surprisingly, it rides like a truck, not a
car.

You can expect a Honda salesman to perhaps
oversell the off-road capability of a CR-V to a
potential customer, just as you can expect a Nissan
salesman to downplay the Xterra's "truckishness," if
the customer seems more interested in comfort than
utility.

At the extremes are the Liberty and the Vue. We've
rounded up examples that are close in price and
equipment for a quick comparison. Both of these
are new models, having arrived just last year.

The Liberty is the replacement for the venerable
Cherokee, which went with only minor changes for
18 years. The Liberty slots between the pricier,
more luxurious Grand Cherokee, and the
back-to-basics Jeep Wrangler.

Our test Liberty is a Sport model, powered by the
3.7-liter, 210-horsepower V-6, which is basically a
six-cylinder version of the Grand Cherokee's
4.7-liter V-8. Both those engines are now available
in the Dodge Ram full-sized pickup, a tip-off that the
Liberty is more truck than car.

The Liberty comes standard with rear-wheel-drive
-- most car-based SUVs have standard
front-wheel-drive -- and our test vehicle had Jeep's
Command Trac part-time four-wheel-drive system.
That means that the Liberty, in normal driving, is
rear-wheel-drive, but if we decide we need extra
traction -- such as we might turning off pavement,
onto the dirt -- we'd tug a lever that engages the
front wheels, and they will help pull the Jeep along,
rather than just roll.

But this is a part-time system, not designed to be
used during normal driving. So when the need for
extra traction ends, we push the lever, and return to
rear-wheel-drive.

Lots of other sport utes, including most car-based
models such as our Vue, have four-wheel-drive
systems that are always engaged. Those vehicles are
usually called "all-wheel-drive," rather than
four-wheel-drive. Yes, it is confusing.

The Liberty also has a separate gearbox called a
"transfer case," that allows for low-range gearing
when you are off road and need lots of extra power.
The availability of low-range gearing is a sure sign of
a truck-based SUV.

This transfer case changes the gearing in the regular
transmission. The Jeep had the optional ($825)
four-speed automatic transmission. When the
transfer case is set to the "high" range, the Liberty
drives along like any other vehicle. But in "low"
range, it still shifts through all four gears, but much
more quickly. In high range, the transmission might
shift from first to second gear at about 25 mph. In
low range, by the time you hit 25 mph, it's already in
fourth. Because of the gearing, your top speed might
only be 35 mph, but the Jeep has been pulling like a
locomotive up to that point, thanks to the change in
gearing. You feel like you can drive straight up the
side of a mountain -- and plenty of Jeep owners
have done just that.

As you would expect, when you drive off-road, you
often encounter stumps and branches and big rocks.
On a truck-based SUV like the Liberty, you should
have plenty of "ground clearance," which is the
distance from the ground to he bottom of the
vehicle. Eight inches is considered decent ground
clearance. That lets you climb over small obstacles
without leaving anything important, such as your
transmission, on the trail.

Those parts such as the transmission and oil pan and
other potentially vulnerable are typically protected
by steel "skid plates," which are just what they
sound like they'd be. Some skid plates are usually
standard on truck-based four-wheel-drive SUVs,
and some of those vehicles have optional off-road
packages that have bigger skid plates.

Our Saturn Vue also has a V-6 -- a
195-horsepower, 3.0-liter V-6. In keeping with our
theory, the Saturn L-Series car also has a 3.0-liter
V-6. Coincidence? We think not!

The Vue comes standard with front-wheel-drive,
but our Vue is all-wheel-drive. It runs along in
front-wheel-drive, but if onboard computers detect
that the front wheels are slipping, as they might on
slick pavement, power is sent to the rear wheels,
and all four wheels are powered until the system
detects that all tires are getting traction. Then it's
back to front-wheel-drive. It works very well. But
even Saturn says on its Web site: "But we don't
recommend attacking concrete-block mountains or
fording large rivers, even if you are a professional
stunt driver." There is no low-range gearing.

For just normal driving, though, either vehicle works
quite well, with plenty of power for passing. The
Vue has one of the best highway rides of any
sport-ute, and handling is exceptional. But it is much
closer to being a station wagon than what many of
us think of as an SUV. Saturn says that, properly
equipped, the Vue can tow a 2,500-pound trailer, if
the trailer has its own brakes.

The Liberty can tow roughly double that with the
Class III towing package, a $245 option.

But its ruggedness and capability has a price. It feels
slightly top-heavy during sharp cornering, and at
highway speeds, the ride can be a bit jarring. There
is a lot of wind noise, likely generated from the big
roof rack.

Mileage is also affected. The Vue gets 19 mpg in the
city, 25 mpg on the highway. The Liberty gets 16
mpg in the city, 20 on the highway.

As with anything, you pays your money, you makes
your choices -- in this case, $24,675 for our Saturn
Vue, $25,315 for our Jeep Liberty.

Is one better than the other?

Absolutely. But which one depends on what you
want.