Here’s the latest reader question, along with my reply!
Devon asks: Is four wheel drive the same thing as all-wheel drive? If not, what’s the difference?
My reply: There is a lot of confusion about this – which has been created, in my opinion, by the marketing people at the car companies. Allow me to elucidate.
In both cases – AWD and 4WD – all four wheels are “driven” (i.e., powered). At least, when the system is engaged. And here we come to the first of several differences.
Most AWD systems are full-time; that is, the system is always engaged – no action needed by the driver to engage the system, which automatically distributes power to both the front and the rear wheels.
Most 4WD systems are part-time; that is, the system is only engaged when the driver selects 4WD (usually, in modern vehicles, by turning a knob or pushing a button). If not engaged, only the rear wheels are powered.
No power is routed to the front wheels.
On the other hand, AWD systems usually – at least, typically – send almost all the power to the front wheels – until slip is detected, at which point the system automatically routes progressively more power to the rear wheels.
Some AWD systems can route almost all engine power to whichever pair of wheels (front or rear) have the most traction; most 4WD systems “lock” the power split in a 50-50 ratio, when the system is engaged.
4WD systems also have a two-speed transfer case, to increase mechanical leverage at low speeds.
Some AWD systems have a similar feature – but without a two-speed transfer case.
4WD systems are “heavier duty” – and designed mainly for dealing with off-road conditions and very deep snow.
AWD systems are lighter-duty, more on-road-minded and in addition to providing a traction advantage, also provide a handling advantage – on both wet and dry paved roads. Unlike 4WD systems – which can only route power front to back – most AWD systems can route power to individual wheels; also, there is no issue with axle bind – the inner wheel turning at a different rate than the outer wheel while cornering – because they can rotate at different rates.
In general, 4WD used to refer specifically to the systems you’d find in a truck or truck-based SUV – while AWD was found in cars and car-based crossover SUVs.
But “4WD” sounds more rugged and manly than “AWD” – and several car companies began (and still are) badging their AWD-equipped vehicles as “4WD.”
It is technically true, but arguably a bit shystery – because AWD is not the same as 4WD.
Ironically, AWD has advantages that 4WD does not – such as the handling advantage already discussed. Just as 4WD has its specific pros – as well as cons.
It’s too bad there’s less precision – and editorial honesty – in the way new cars are marketed nowadays.
. . .
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