I was hoping to read the comments here to understand once and for all what the difference between AWD and 4WD is.
I'm still as confused as I was before reading the comments. It appears the answer is...it depends on the manufacturer/vehicle.
I'm still as confused as I was before reading the comments. It appears the answer is...it depends on the manufacturer/vehicle.
What we can decipher is what the NPS is angling for. Many cars labeled "AWD" provide power to all four wheels, but if one of the wheels is not making contact with the ground, the remaining ones get little or no power. This is because the axles incorporate differentials - and if you have uneven traction, the torque delivered to the differential follows the path of least resistance. The end result is that it's deceptively easy to get stuck on uneven terrain, in mud, or in snow.
But then, some "AWD" cars actually provide good workarounds. In the simplest variant, the car automatically applies brakes to the free-spinning wheel, forcing the differential to power the other wheel. Less wasteful and more responsive solutions that mechanically sense torque imbalance also exist.
And then, some "4WD" cars work roughly the same way! For example, some models of RAM 3500 are labeled as four-wheel drive (4x4), but rely on torque-sensing ("Torsen") limited-slip differentials. Other 4x4 cars might have a button to physically lock the differentials. This is widely regarded as the best option, except it's dangerous on paved roads (and makes turning hard).
AWD generally does not mechanically 1:1 interlock anything, instead using things like torque converters. This allows it to be used on clean pavement. It isn’t as robust as 4WD, and has to respond to wheel slip instead of simply being 1:1 all the time.
> The most consequential distinction between AWD systems and more capable 4WD systems is that most vehicles equipped with 4WD have one or more locking differentials that massively aid in off-road traction. While AWD systems are great for increasing driver confidence on slippery road surfaces and in light off-roading, they are easily flummoxed in more challenging off-road terrain, especially low-speed and low-traction situations.
I agree with the other comment: if the Parks Service wants locking diffs (or ride height or whatever else) they should say so, not rely on inconsistent marketing terms.
- When you have two wheel drive you only have one differential between the two wheels. - When you have four-wheel drive you have three differentials, one between the front wheels, one between the rear wheels and one between the front and rear. So far so simple.
Now one of the problems with differentials is that if one of the wheels loses traction, it gets all the power back and spins in a vacuum.
Finding yourself with a wheel in the sand, in the air, on the snow, etc. is very common when driving off-road or in the mountains. This problem has been solved with the differential lock, which can be manual or automatic. When locked, the differential is locked and power is transmitted equally to the wheels. So you can get out of your sandy or snowy hole. That's what we call a 4x4.
A All-wheel-drive has no differential locking system.So if one wheel loses its grip, the vehicle is stuck. There's nothing you can do - all the power will go to the wheel with the least grip.
So AWD is particularly unsuitable for off-road use and shouldn't be sold as such.
Some off-road vehicles do not have a differential, such as quad bikes or buggies. Perfect for mud, not so great on the road.
https://en.wikipedia.org/wiki/Differential_(mechanical_devic... https://en.wikipedia.org/wiki/Locking_differential
A proper locking differential found in most traditional 4x4 vehicles/trucks, when engaged, physically locks the axles together which means they cannot spin at different rates. This is essential for many more rigorous off-road applications when you may have to rely on traction from a single wheel to get you unstuck.
This is exactly the type of misleading marketing that is described in many other comments. A clutch pack cannot physically lock axles together in the same way as a locking diff.
Subaru for example has had adaptive AWD since early 2000s.
There are a few other systems (not 25k), using a clutch or independent motors, but it doesn't matter: the claimed deficiencies of some AWD only needs to be debunked and corrected.
Watch the linked YouTube video for more details on Subaru's system, the same system cited by the National Park.
Bottom line, a lot of modern AWD systems are perfectly adequate and in some cases superior to 4 wheel drive systems.
Now that we have knobs for different "driving modes," the the ability to slam it into whatever position whenever we want while an ECU figures out how to keep a gearbox from exploding, it's genuinely hard. Still, the presentation of a setting like "lock/unlock" and "two/four" and "high/low" is the standard I still go by (right or wrong).
it's more useful to consider what people suggest for a track.
- "you're going to need a diff lock"
- "you're going to need high clearance"
I agree, and I know a bit about this!
The reality is very few vehicles on the market are legit "off-road" capable. But, the other side of that is not every trail is legit "off-road", either. Just because there's no pavement, doesn't mean it's "off-road".
There's an entire spectrum of vehicles and trails where normal people can get off the beaten path.
https://www.youtube.com/watch?v=Jk246sutET0
At a very simple level it boils down to: Do you have a transfer case? If yes, then it's a 4WD.
& the marketting department.