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2WD Vs. 4WD

Do you really need four-wheel drive?

If the world of off-roading calls-out to you, and you're ruing the limitations of your two-wheel-drive light truck, then read on. While 4x4s are the kings of rock crawling, mud bogging and all other sorts of non-paved adventures, you don't have to scrap your reliable 4x2 in order to join in the fun. By simply adding a few upgrades, you and your 2WD may be able to respond to that call of the wild.

Closing the Gap

Ten or 15 years ago, the choice between two- or four-wheel-drive light trucks involved some serious thinking. Although tempered by the fact that the off-road models held their resale value in direct proportion to their less expensive 4x2 counterparts, at least on a regional basis, the cost of 4x4s was higher. To further complicate matters, the 4x4 option at that time came with some noticeable downsides: harsh rides on paved roads and heavier weight, resulting in lower gas mileage and less highway horsepower.

With the growing popularity of light trucks in the form of both pickups and SUVs, manufacturers realized that this vehicle category was being used in a broader range of driving conditions than before. The result of this realization is a wide truck selection that appeals to today's driver, and a narrowing gap between two- and four-wheel-drive features.

Today, some of the larger heavy-duty trucks come with the same suspension systems loaded on their 2WD and 4WD models. The only real remaining differences are the inclusion of differentials on the front wheels of 4x4s and the availability of lower gearing and higher low-end torque in the 4x4 mode—a plus for tow vehicles, regardless of whether or not they ever actually encounter off-road driving conditions.

Modifications

So what sort of modifications will breathe new life into your trusty 4x2 and open up new off-road capabilities? Look at the 4x2 Toyota Prerunner, a phenomenon modeled after the two-wheel-drive trucks used to pre-run desert races. Having to cover the same terrain as the actual race trucks, they are not obligated to do everything that the race trucks are capable of. You may also consider that the famed Paris-to-Dakar rally now has a category for two-wheel-drive vehicles.

The ability to take a 4x2 off-road boils down to attaining two simple, necessary factors: ground clearance and traction. Lift kits—designed to provide that extra clearance for oversized tires and to avoid gutting your undercarriage on rocks while still maintaining steering and braking geometry—are available for 4x2s. With the availability of lift kits and other suspension upgrades, you can now put a system together that is tailored to your own, personal off-road requirements without having to compromise highway comfort.

The same holds true for tires that are intended to provide you with the traction you need. With the variety of off-road competitions, each requiring a specific tire design and tread, the only limitation is your wallet. BFGoodrich, with an unchallenged success rate for both Baja and Paris-to-Dakar rallies, markets a heavily treaded tire designed as the rear tire for two-wheel-drive desert racers.

One possible additional option for two-wheel-drive truck owners is an effective locking system for the differential. A number of 2WD and 4WD pickups have limited-slip differentials that lock-up the axle when a wheel starts to slip. When the axle is locked, full power is delivered to both wheels.

Limited Slip

If what you have just read has left you scratching your head with confusion, here's an explanation of slipping and non-slipping differentials in simpler terms: When turning, the wheel on the inside of the turn is traveling a shorter distance than the wheel on the outside of the turn. The differential allows the two drive wheels to rotate at different speeds by sensing the amount of traction on each wheel. In the case of a turning vehicle, the inside wheel has more weight or traction, so the power goes to the unweighted wheel.

Now, consider what happens when those wheels get stuck in mud or loose sand. The wheel with the least amount of traction gets all of the power, but since it doesn't have a bite into the surface of the road, the vehicle simply spins in place.

Limited-slip or automatic locking differentials are usually sufficient in very light off-roading situations, but they are not a substitute for a manual locking system. With a manual locking system, you can lock-up your differential at the base of a steep grade or right before you slog through mud or sand—or at any other time of your choice for that matter. While most manual locking systems are marketed to hardcore off-roaders, they can effectively pull a 4x2 through 4x4-sized conditions about 95 percent of the time. If you're worried about that remaining five percent of time, then you really do need a seriously modified 4x4.

These modifications are not cheap and, with the exception of tires, they are a bit beyond the skill level of most shade-tree mechanics. If you have to choose, however, between buying a new 4x4 vehicle, or adding upgrades to a trusty 4x2, the latter will add brawn to that 4x2 at a fraction of the cost of buying a new 4x4.