A long time ago, I used to drive a green Land Rover Series III around with a sticker in the rear window that read "The Best Four by Four by Far." An extremely optimistic slogan, to be sure, and something of a case of pride goeth-ing before the fall.
Still, even though the little Landie had a tendency to shed parts in a sort of automotive leprosy, it was pretty sure-footed in poor weather conditions. You had to stop the thing and get out to manually lock the front hubs, but once they were in place, all hundred or so remaining horsepower could be unleashed and off you went to interfere with the simple quests of Kalahari bushmen or what-have-you.
These days, I drive a Subaru, and you don't really have to do anything when it starts snowing except repeat the mantra, "I'm not really a rally driver so I should probably slow down," and promise your spouse that you certainly won't be attempting manoeuvres like the Scandinavian Flick. Nope. Not a bit of it. Perish the thought.
The Subaru is an allwheel-drive vehicle rather than a 4x4 - at least, that's what it says on the back.
Yet in both cases all four wheels are being driven, so what's the difference?
Even further back than the emphysematous Land Rover, most cars were twowheel drive. Four-wheel drive was only for the slippery stuff, and involved manually locking the hubs as previously mentioned. Most systems also had a low-range gearbox for increasing low-speed climbing capabilities; in the Land Rover, this involved putting the car in neutral and fiddling with a pair of yellow and red floormounted levers, usually while saying things like, "go IN you bast-"
Um. Usually while shouting encouragement. Yes.
The change in this process came with the Landie's snootier cousin, the Range Rover. Early Range Rovers had a lockable centre differential, allowing the front and rear wheels to turn at different speeds on a dry tarmac surface.
Drive a locked-up four-wheel-drive car on pavement, and you can feel the front wheels scrub when you go around a corner. Just as the inside tires turn fewer times in a bend than those to the outside of a corner, the wheels in charge of steering need to spin at different rates than those out back.
However, the Range Rover still had the ability to lock everything up and came with a crawling gear for getting out there in the wilderness and shooting some of it in the face. It was still a proper fourwheel drive.
The next car that came along was perhaps the first crossover: the AMC Eagle. The Eagle didn't have a low-range gearbox or a lockable centre differential, but they called it a 4x4 anyway.
Pretty much here is where marketing got involved and the nomenclature went to hell in a four-wheel-drive handbasket. Audi came along with its Quattro system and called it allwheel drive. Fiat came along with a transverseengined car and called it the Fiat Panda 4x4. Other companies called their systems 4WD or AWD.
Currently, there are any number of branded systems available from BMW's xDrive, to Mercedes' 4Motion, to Subaru's vaunted Symmetrical All-Wheel Drive. Given that every single manufacturer offers some sort of car-based crossover, hardly any of these systems are a true four-wheel drive in the original style. Most are so married to various electrically controlled traction systems that it's less the mechanical bits that are important as much as a host of electronic brains.
Basically, a "real" parttime four-wheel-drive system is usually found in a body-on-frame truck like a Nissan Xterra. These are rear-wheel-drive vehicles where the front wheels are engaged via a manual centre differential, but shouldn't really be used except on snow or gravel. It's the most rugged system, but not useful in the wet, and usually the least fuel-efficient.
When a vehicle is derived from a frontwheel-drive application, the system most often only connects the rear differential under slippage. These are the so-called "slip-and-grip" setups, though some lock up at low speed or under hard acceleration automatically, before the tires lose traction. Depending on the electric control type, these are the light duty option and provide the best fuel economy. However, their part-time nature can make them less effective.
The all-wheel-drive systems that Mercedes and BMW use are built from rear-wheel-drive cars, and have the ability to send more than half the power to the rear for better handling. In something like a BMW 3 Series, the all-wheel-drive car has better grip, but adding the drive to the front slightly reduces steering feel versus the rear-drive-only model.
Lastly, we have the systems used by Subaru and Audi, where the differentials are integrated right into the transmission housing. It's important to note that Subaru's "Symmetrical" all-wheel drive is balanced side-toside, not front-to-back. The high performance STI has an adjustable centre differential that can be tweaked for more tail-happy rear bias.
A Forester is usually front-drive biased in its automatic transmission application. However, all wheels are being driven at any one time, giving a better planted feel than the part-time systems, but with slightly poorer fuel economy.
Which is best? Like anything else, it depends what you're using it for. Given our mild, frequently damp West Coast climate, most of the time a simple transverse engined all wheel drive will provide all the extra traction needed. Track day enthusiast with a year-round daily driver? Maybe something with a greater rear-drive bias will suit.
But let me end by saying this. No matter how good these systems get, from the incredible tarmac-shredding Nissan GTR to the go-anywhere Jeep Rubicon, not a single one of them will outperform a 10-year-old Honda Civic (or similar basic front-driver) if the Civic's got proper winter tires on when the snow starts flying. That "best Four by Four by Far" sticker is going to look pretty dumb on a truck that's getting pulled out of a ditch.
Brendan McAleer is a freelance writer and automotive enthusiast. If you have a suggestion for a column, or would be interested in having your car club featured, please contact him at [email protected]. Follow Brendan on Twitter: @brendan_ mcaleer.
