[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.