Rain and "full-time AWD"

Hmm. I would have thought when it slipped since there is no differential action when all 4 tires are spinning at the same speed.

 

We had one Land Rover Discovery with a non locking center diff with low range, and a second Discovery where we paid for the locking diff as an option. But it wasn’t too long ago that a locking center diff in a full-time 4WD was considered esoteric.

 

Do those have a 2 speed transfer case? Just trying to see if there's anything consistent.

 

Single speed.

There’s another wrench in the works…GM offers part time 4wd trucks without low range unless you purchase the offroad package.

 

The people who made transfer cases for Chevys and Dodge were the same people, NP-something or another.

Fun fact, NP stands for "New Process".

*Edit* - not Fords

 

Maybe we’re talking in circles here and are both saying the same thing. When you say “slip” what do you mean?

 

One axle with traction and the other without causing different prop shaft speeds. However is says in the link 40/60 when driving straight.

 

No, those are AWD

 

Think of it this way. Every 4WD vehicle is an AWD vehicle. Because both 4WD and AWD send power to all four wheels. But not every AWD vehicle is a 4WD vehicle. Why is that? What is the difference that makes 4WD a special kind of AWD?

The difference is that the 4WD version locks the front and rear axles together, creating tractor-like performance that continues unperturbed by the varying levels of grip at each axle. AWD in contrast allows power to flow back and forth between the axles, which is undesirable when it results in extra power being sent to the axle with less grip.

This is how the terms are most commonly used in the marketplace. AWD is used to refer to all the permutations of systems that shuttle varying amounts of torque from front to back. Like your standard crossover.

But 4WD is reserved for those vehicles that do something special when they send torque to each axle: they send it in a fixed split that will not vary regardless of the terrain, creating the tractor effect.

Thus, the Limited is in truth an AWD vehicle in normal use and a 4WD vehicle when you lock the center differential.

 

Early 2000's Land Rover Discovery 2, 1950s to 1970s Land Rover Series. Have 2 speed transfer cases and no locking center diff

 

I guess we’ll just have to agree to disagree on this. I maintain that a vehicle is full time 4WD whether the center diff locks or not.

But we can still be friends!

 

Those vehicles are AWD. Those are vehicles designed for ON road performance.

 

You would be correct.

If a vehicle has low range, it's intended for off-road use, hence "4WD".

 

I would think a vehicle should at least have to have a low range, or center differential lock to be considered "4WD".

It would be nice if the manufacturers had some consistency on this.

 

There is a lot of overlap in terminology. Thank the marketing departments for that. A permanent center diff is the same thing as AWD. But some manufacturers call it 4WD... or "full time 4WD". Either way its... 4 wheels driving

Whats really crazy is when one manufacturer uses both terms on the same system offered in different generations. Honda is an example. The Pilot used to be called "full time 4WD" and then when they redesigned it for 2016 the naming became "All wheel drive" But the funny thing is the actual mechanicals didn't really change AND are NOTHING like either a multi-range transfer case part time 4wheel (Runner) or a center diff AWD (Audi/Subaru) system.. Its actually a FWD biased setup with a permanently locked single range center transfer routed to an electronic clutch pack rear "diff" that selectively engages and disengages the rear wheels and apportions side to side torque based on slip sensors. Ultimately its a FWD car with electronic rear traction all that changed with the naming was they made the software logic more aggressive in how and when it biases torque to the rear


(Disclosure: we have owned both generations of Pilot's in my household along with the 5th get 4R, 2nd gen Tacoma, FWD/ RWD sedans, etc so I've had first hand experience driving them all over the years ....)

 

The theme of inconsistency continues.

If it were up to me to define, I would say that a system that defaults to 4wd, regardless of power distribution, should be considered full time 4wd. And, a vehicle that defaults to 2wd, only sending power to the other axle when slip is detected, should be considered AWD. With all of the inconsistency, this definition would at least make some sense to me.

But, that's just my opinion. And, we know how much that's worth.

 

FWIW, Wikipedia has a discussion of the terms AWD and 4WD here: https://en.wikipedia.org/wiki/Four-wheel_drive

Of note, this piece agrees there's a lack of clearly set definitions and lines. To wit:

Four-wheel-drive systems were developed in many different markets and used in many different vehicle platforms. There is no universally accepted set of terminology that describes the various architectures and functions.[1] The terms used by various manufacturers often reflect marketing rather than engineering considerations or significant technical differences between systems.[2][3]SAE International's standard J1952 recommends only the term "all-wheel drive" with additional subclassifications that cover all types of AWD/4WD/4x4 systems found on production vehicles.[4]

Thus my point that 4WD is a subset of AWD, denoting an AWD system with special characteristics.

In that regard, the discussion includes the following, which supports the arguments that several of you have made in this thread:

Four-wheel drive (4WD) refers to vehicles with two axles providing torque to four axle ends. In the North American market, the term generally refers to a system optimized for off-road driving conditions.[7] The term "4WD" is typically designated for vehicles equipped with a transfer case that switches between 2WD and 4WD operating modes, either manually or automatically.[8]

.... When referring to heavy vehicles, the term is increasingly applied to mean "permanent multiple-wheel drive" .... on systems that include a differential between the front and rear drive shafts.[11]

...When used to describe AWD systems in light passenger vehicles, it refers to a system that applies torque to all four wheels (permanently or on-demand) or is targeted at improving on-road traction and performance (particularly in inclement conditions), rather than for off-road applications.[7]

If 4WD is thus an AWD system that is more intended for off road use, then the question becomes: what are the features that make it more suitable off road? I think it's clear that the two main features that accomplish this are locking differentials and a low gear.

QED: your AWD vehicle is also a 4WD vehicle if you can lock one or more differentials and engage a low gear.

 

Amen.... And add to the fact that 90% of the people who buy them (and 99% of salesmen selling them) have no idea what the differences are between a locked transfer case, an open center diff, a mechanical limited slip diff, and electronic clutch pack - and you have a recipe for chaos.

Which is why we have folks that join vehicle forums and the first post is... "I bought a Wrangler Rubicon Unlimited Extreme Edition why is it dragging the front wheels when I engage 4H on the road?" or " I bought a 4Runner TRD Pro, why does it want ot spin out so bad on ice?" I am a mechanical engineer by education and was raised by a dad who is a lifetime gearhead and taught me how to wrench before I was old enough to drive the lawnmower so I'm probably biased ... but I would think spending 50 grand would inspire people to do a little research first......

 

Nope.

How are we supposed to keep debating this if we all agree?

It seems that AWD and 4WD are different terms that generally mean the same thing (except when there are more, or less than 4 wheels).

Maybe part time VS full time is the biggest distinction?

 

I wish my TRDP had a full time 4wd selection like the 4th gen V6 did.

 

This can't work. We'd end up having craptastic crossovers called 4WD just because you have to push a button to get it to switch from econo-box FWD to some half-ass form of AWD.

Per my post from this morning, "4WD" is most associated with off road ability. So the features that make an AWD vehicle a 4WD vehicle must be there for off road ability. Thus, yet again, a locking differential is the single most important differentiator, with option of a low gear a second key differentiator.

 

No idea why they dropped that option. I love my limited for that feature. My 2020 OR was great, but having the full time 4WD means almost never having to touch the transfer case selector knob.

 

Hey, I got the idea from something in one of your posts!

 

The more I think about this, the more I think I would prefer to have full time 4wd again as well. It was definitely superior in winter.

 

Well with the V6 you had to shift into full time because it still had 2wd. Some of the 3rd gens were the same and Mitsubishi had a pretty advanced 2wd/Full Time/Part Time system in the Montero. It was called Super Select.

The V8 runner 4wd didn't have 2wd.

 

No way, you're gonna have to prove that. I've been consistent that 4WD is a form of AWD where there's a locking diff. I also posted on this months and months ago on another thread. That was in the context of the Limited -- what kind of system it has. My point then, and now, is that it's called "full time 4WD" because it is an AWD system with the ability to lock the diff. That it is AWD by default gives it the "full time." That you can lock the diff makes it 4WD and not just AWD like your average crossover.

Some people have made the case that a low gear should also be required. I don't have strong feelings about that either way, but certainly the presence of a low gear means more off road ability, which as per the discussion regarding the Wiki article seems to be the primary differentiator, in common parlance, between 4WD and AWD.

 

I think the line of demarcation between AWD and 4WD is the transfer case.

It looks like we’re not going to resolve this issue here. Perhaps it would be better just to step away from this thread and let it descend into the depths of obscurity.

But just know — you guys who call your 4Runner “AWD”? I’ve got my eye on you…

 

never!

 

No way! It's better to debate it to death, and then still not agree.

Nope. It's more fun to keep talking in circles.