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The 4-Wheel Drive
Uses of the Popular 4WD
by Jim Walczak
The
first digit in a "wheel-drive" equation refers to the number of
wheels. The second digit refers to the number of driven wheels.
· 4 x 4 (four by four): A vehicle with
four wheels that's powered by four wheels (4WD)
· 4 x 2 (four by two): A vehicle with four
wheels that's powered by two wheels (2WD)
Today's
vehicles offer a number of different drive train systems designed to help out
in slippery conditions.
For
example, a four-wheel drive vehicle may come equipped with "Full-time
4WD", "Part-time 4WD", or "Automatic 4WD".
4WD
Modes
Here's
what you should know about each, and when you should actually drive in 4WD mode.
In
general, 4-wheel drive refers to a vehicle's drive train system that can send
power to all four wheels, but the four wheels are not necessarily under power
all at the same time.
Here's
an explanation of the different types of four-wheel drive systems:
· Full-time 4WD (or permanent 4WD) means the
vehicle is constantly providing power to all four wheels, usually with power
being shifted between the front and rear axles as needed.
This provides maximum
traction in both dry and slippery driving conditions and requires no action
from the driver to activate it.
IMPORTANT: Full-time 4WD doesn't provide as much mobility off-road as
part-time 4WD does, because the system is designed such that it allows a set of
wheels (front or rear) to spin if they don't have traction.
· Part-time 4WD refers to a vehicle with
selectable 4x4 or 4x2, requiring the driver to manually shift between 2WD and
4WD using either a lever or a switch.
With part-time 4WD, you
can "shift on the fly" (switch between 2WD and 4WD while driving).
Part-time 4WD gives you
better traction on slippery surfaces because the front and rear sets of wheels
are locked together. Thus, this is the optimum choice for most off-road conditions.
IMPORTANT: Vehicles with part-time 4WD systems should not be driven on dry,
smooth road surfaces when in 4WD mode, or you will soon be spending a lot of
money on repairs.
· Automatic 4WD is a full-time system that lets
the vehicle operate in 2WD (either front or rear) until the system judges that
4WD or AWD is needed. It then automatically routes power to all four wheels,
varying the ratio between front and rear axles as necessary.
Usually, a slipping
wheel activates the system. However, some of the more sophisticated systems use
software that switches the system to 4WD or AWD during specific driving
conditions — BEFORE a wheel begins to slip.
IMPORTANT: Automatic 4WD vehicles are not recommended for serious
off-road driving because all four wheels are powered at all times, which is not
wise under certain off-road conditions.
To
determine which type of four-wheel drive your vehicle has, consult your owner's
manual. There you should also find additional information with regard to
driving your vehicle in 4WD mode.
The
gearing options found in 4WD vehicles help a
vehicle tackle many of the unique situations encountered while driving off-road.
Following
are a variety of conditions in which you would want to use 4WD to avoid sliding
or spinning.
Hi
Range 4WD
4H
allows you to drive full speed, if necessary. The high range ratios in 4WD mode
are the same as the gear ratios in 2WD.
Here
is when to use 4H:
·
for
traction when the area isn't steep
·
when
stuck in the sand
·
extremely
slippery conditions
·
snow
·
ice
·
rocky,
gravel roads
·
gullies
·
extremely
muddy areas
·
ridges
Low
Range 4WD
4L is
for creeping along at slow speeds. It reduces the strain on your vehicle, just
remember to stay below 25mph in low range.
While
it does not provide more traction, it does provide 2-3 times more torque at
about 1/2 or 1/3 of the speeds in high range. Low range gear ratios are
approximately half that of high range. Here is when to use 4L:
· on
wet, slippery surfaces
· passing
through sandy areas
· on rough trails
· through
shallow water
· rock-climbing
· climbing
steep hills
· through
mud
· descending
steep hills
Additional
Tips
· Don't
change gears in the middle of a water crossing, going up or down hills, or in
sand dunes.
· Be
prepared: Engage low-range 4WD before you need it.
· Don't
operate 4WD on hard dry surfaces.
· When
in doubt, use a lower gear!
Jim Walczak
Publisher
and writer of Jeep Guide website
Member
of BlueRibbon Coalition
Experience
Jim
Walczak is a former writer for ThoughtCo and contributed work for over seven
years. He has been a Jeep and off-roading enthusiast for over 15 years.
His current pride and joy is his '04 Jeep Wrangler Unlimited TJ. Jim
is a member of the BlueRibbon Coalition, an advocacy group that promotes
motorized access to public lands and waterways. In his free time, Jim can
often be found venturing off-road along the backcountry roads of Tennessee,
always choosing to follow the route less taken.
Jim is
the owner of Squeaky Wheel Marketing, where he does marketing and public
relations and is responsible for new sponsor development for Hoosier Thunder
Motorsports, a multi-car drag racing team on the NHRA and IHRA racing
circuit.
Education
Awards
and Publications
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and Dotdash
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