[COGlory]

While there are rare situations where locking differentials are meaningful, having been in many hair raising off-road situations, including a real life or death one, I'd much rather have AWD and clearance, than 4WD and no clearance.

That is to say, I'm not convinced by the article's hypothesis about locking diffs. It's extremely rare to need to deploy those: beached, or slow starts up vertical surfaces like boulders. An AWD vehicle with good tires and good clearance is really quite good. Bonus points if you don't care about wrecking it.

[lamp_book]

> 4WD and no clearance

I think I've only really seen this as a Honda Element - otherwise I'm not sure it meaningfully exists. The reality with most AWD cars is that their important guts are hanging lower compared to 4WD trucks even when the paper ground clearance is similar.

My previous car was AWD and I have a 4WD SUV now largely for off road performance, and there's no question 4WD (particularly 4LO) is much better at getting unstuck in trail conditions. The AWD is definitely superior for icy pavement in the cold months though.

> Bonus points if you don't care about wrecking it

This was actually what mainly pushed me over to the 4WD side instead of something like the Forester. The crossovers can actually get you to a lot of places but they do get thrashed if you do it enough. They are still more geared for pavement use but, if you're wrecking your suspension off road, the on road performance isn't gonna be great either.

[toast0]

> I think I've only really seen this as a Honda Element - otherwise I'm not sure it meaningfully exists.

Maybe it's not meaningful, but vans in the 80s and 90s were often offered with optional 4x4, sometimes with a locking differential. An unmodified Astro or Aerostar doesn't have a whole lot of ground clearance, but could fit the definition of 4wd if properly optioned and probably wouldn't be suitable for these trails unless it gets some aftermarket help.

Of course, few of these are running anymore. 4x4 kei vans can get pretty serious too, but not a lot running on US national park fire roads.

[ADSSDA]

> I think I've only really seen this as a Honda Element

What Honda element had 4wd? As far as I'm aware they were all (a pretty bad) AWD system.

[lamp_book]

They marketed it as 4WD anyway.

[soganess]

I'm working from memory here, but I believe early 90s Audi "quattro"s (like the 100) had the feature. That said, I think we are very much in "the exception that proves the rule" territory.

[NDizzle]

What 4wd vehicle doesn’t have good ground clearance?!

[jofer]

Most stock pickups, actually. You'd be surprised how low the clearance is on a stock f150 without the various off-road packages. I.e. you can easily have a pickup with basic 4wd but only 8 inches of ground clearance. That's technically "high clearance", but not by much, and the poor approach, departure, and break over angles make it tough too.

[ghaff]

Depending on your definition of "good," probably most of them. While I have been guilty of taking questionable AWD rentals on questionable roads in places like Death Valley when younger, you really want properly-equipped Jeep Rubicons and the like that you're not going to get from the average car rental place.

[ezfe]

Subaru Impreza has less than 8 inches of ground clearance, which is the threshold they use in the link.

[garciansmith]

Imprezas are AWD, not 4WD, like all Subarus (well, the BRZ is RWD). The whole point of the article is that there's a difference!

[tom_]

First generation Subaru Justy.

[kube-system]

Suzuki X-90 ?

[COGlory]

None, which is my point. I'm trying to say I suspect it's ground clearance, not locking differentials that matters on these roads.

[relaxing]

It is both.

[Zandikar]

> That is to say, I'm not convinced by the article's hypothesis about locking diffs.

I'm not an offroader, but I did own a vehicle without a locking diff, that I later upgraded to having a locking diff (slapped a G80 on the rear of an 80's GMC Sierra) and that made a huge difference even on pavement in inclement weather. Granted, that was a RWD pickup with very little weight (typically) over the drive wheels. I'd honestly be shocked if the impact was minimal in truly offroad conditions. Granted, that's RWD which is even less than AWD or 4WD, so by no means apples to apples comparison there, just my 2 cents.

That said, this isn't a binary thing (locking vs open). There's a wide variety of AWD technology out there, and I could nerd out on the specifics, but at the end of the day, some are very limited in their ability to send power to one set of wheels vs the other, and may not have locking/limited slip diffs at all, and just use brakes to prevent wheel spin. I will say, Subaru (especially the higher/sportier trims like WRX/STi) can often hang and even shame some 4WD vehicles in some conditions. There's no shortage of videos of Subarus helping a 4WD out of a jam, or completing a course they could not, but how much of that is a function of their specific AWD tech and limited slip diffs vs proper tires and lighter weight and any number of things is a matter of debate that I'm not qualified to weigh in on. Again, am a gearhead, but not an offroader.

So I suspect it's not so much the Park saying "Subaru/AWD can't cut it" but rather, keeping track of which years, brands, models, trims, and/or potential optional equipment does cut it is a much more massive headache to keep track of and verify than just saying "4WD yes, everything else no", and I can't really fault them for that.

[pandaman]

I am not an off-roader by any stretch of imagination, but I figure the AWD works like single axle drive with a simple diff on each axle i.e. if one wheel has no traction then all torque goes to that wheel and zero goes to the opposite one. I once got stuck on pretty solid pavement in a RWD car when one rear wheel hanged off a curb and lost traction, after that the car could not move as the only wheel getting torque was the one hanging off the ground. I figure the other axle would still get torque on an AWD as they usually have some kind of limited slip mid diff effect from whatever scheme they use to distribute torque between axles, but if you hanged out a wheel on each axle then an AWD vehicle would become stuck too?

[nucleardog]

Depends entirely on the AWD system.

Many will do what you’re describing—getting a front and rear wheel off the ground at the same time will leave it stranded. A limited slip center differential will ensure if one axle loses traction the power goes to the other, but many vehicles cheap out and have open differentials on each axle, meaning when one on each axle loses traction it’s just spinning wheels.

Some vehicles have limited slip front/rear/front+rear differentials that avoid this issue. Many newer vehicles simply use the traction control and brakes to avoid it—if a wheel is spinning, it applies the brakes to provide resistance and redirect some torque back to the other wheel.

Like many others are saying, “AWD” is such a broad term as to be basically meaningless.