[Samurai]

GV has open rear and front diff. Can't be locked. The center LSD is torque sensing, same as Fortuner. That is why I am saying Fortuner has the exact same 4WD system as GV.

[karpusv]

Fortuner here has lockable center differential with Torsen LSD. Rear differential is the normal (open) type. However, certain regions like UAE and others have Fortuner with lockable rear differentials also

[Sawyer]

Good, now we have a thread where we can wallow in this stuff!!
Here is an example of how the industry has made things very confusing by inconsistent, and even plain wrong terminology.
A Torsen LSD. What is L about it? It is a mechanical device that is torque sensitive, so Torsen. And it is a differential like any other open differential. Left open, it will channel all torque via the line of least resistance to a wheel with zero traction, as, for example a wheel that is no longer in contact with the road has. On an axle, it will do this by denying the grounded wheel of any torque. In the center, it will do this by denying the other axle of any torque as well. Which is why in a 4wd car with an open center differential, complete loss of traction on just one wheel, will result in all the torque flowing to that wheel, leaving it spinning furiously in the air, leaving the 4wd car stuck. While a 2wd car will still make progress, if that wheel is not on the driven axle! Which can be the cause of a good auto trivia question.
So, what is limited about this differential? And why then call it Torsen LSD?
And of course there is all the other stuff - AWD, real time 4WD, full time 4WD and many other terms that get applied in inconsistent ways by the marketing guys writing the brochures. Of course the one good thing is as is true in all professions, the geeks on the subject like those writing this can assemble around the jargon, keeping the rest of humanity that does not care much about that profession, totally bemused!

[Samurai]

Originally Posted by Sawyer

A Torsen LSD. What is L about it? It is a mechanical device that is torque sensitive, so Torsen. And it is a differential like any other open differential. Left open, it will channel all torque via the line of least resistance to a wheel with zero traction, as, for example a wheel that is no longer in contact with the road has. On an axle, it will do this by denying the grounded wheel of any torque. In the center, it will do this by denying the other axle of any torque as well.

Are you describing Torsen LSD or just open differential? Because you just described open differential.

Torsen LSD acts like open diff only when both sides have same traction. If one side loses some traction (beyond a threshold), more torque is instanteneously delivered to the other side, the side which has better traction. Read this: Torsen - Wikipedia, the free encyclopedia

[Sawyer]

Originally Posted by Sawyer

Thank you for making my day!

If the power lever was just a label, it would only be funny. But I suspect it gets used like that - I remember reading on a Safari thread that the showroom folks had no hesitation in running the Safari, a part time 4wd without a center diff, in 4wd mode on tarmac. In many other instances, this must be happening, at the hands of owners who do not know these things as well as they ought to. Taking the case of the Safari as an example, maybe some of the owners' transmission issues are self caused.
Has anyone posted of such self sustained drive line failures on their cars anywhere on the forum?

[Sawyer]

Originally Posted by Samurai

Are you describing Torsen LSD or just open differential? Because you just described open differential.

Torsen LSD acts like open diff only when both sides have same traction. If one side loses some traction (beyond a threshold), more torque is instanteneously delivered to the other side, the side which has better traction. Read this: Torsen - Wikipedia, the free encyclopedia

Hmm, now I know where you are coming from, it is the same story of imprecise jargon that abounds.
Here is a cut paste from the site referred.
Quote
The Torsen differential works just like a conventional differential but can lock up if a torque imbalance occurs, the maximum ratio of torque imbalance being defined by the Torque Bias Ratio (TBR)
Unquote
As you will see on the site, this Torsen referred here is a patented product that will lock up on its own if wheel resistance is sensed to change beyond a point, without user intervention to do so. And this one is a special kind of center diff, that the LC has.It is probably expensive. But I am pretty sure the Fortuner does not have this one, I doubt the GV has it, and I am sure the Pajero does not have it.
And some companies have gone and trademarked a word that is also a generic - Torsen.
By definition, in generic terms, any open differential is torque sensitive and therefore a Torsen diff. Which description has slipped into usage as Torsen LSD. I think you will find this somewhere on the web too!

[Samurai]

Originally Posted by Sawyer

It is probably expensive.

Center LSD is indeed very expensive, I have heard it alone costs 6L on the GV.

Originally Posted by Sawyer

But I am pretty sure the Fortuner does not have this one, I doubt the GV has it, and I am sure the Pajero does not have it.

After digging around the web for a long time, I had discovered that GV has torque sensitive LSD. Since you doubt that, do you have any alternative suggestion about what kind of LSD is present in GV?

The chief engineer for GV thinks it is torque sensing LSD: http://www.globalsuzuki.com/grandvitara/dev.swf

[Sawyer]

I think it is a torque sensitive differential. Which does not have a limiter that will prevent all the torque from flowing to a wheel that has zero traction. And to limit that from happening, is why you have to engage the 4HL mode.
I am sure about the Pajero's SS II transmission of course, which also has the torsen differential at the center. But it does not have a torsen LSD. Saying that for the Pajero would definitely be the same misnomer I referred to earlier. For the GV, I have not studied in depth what it has, but the presence of the 4HL position would suggest to me that its the same.
PS: The Pajero's center diff is also what adds to its cost - but I think that the one that the LC has, that does limit the torque even in open mode if what the brochure says is correct, would be one of the many reasons for its astronomical price tag.

[Samurai]

Originally Posted by Sawyer

I think it is a torque sensitive differential.

But not torque sensitive LSD? Now aren't you trying to create new jargon?

[Sawyer]

Originally Posted by Samurai

But not torque sensitive LSD? Now aren't you trying to create new jargon?

Am I? I would think that distinguishing between torque sensitive differentials, and torque sensitive limited slip differentials is not just creating new jargon. When both exist in the automotive world as two different products.

A good site to read for people that want to revisit fundamentals is the how stuff works write up about differentials. It clarified things very well for me. The only confusing thing to my mind was the thing that about open differential always applying the same amount of torque to each wheel. Took me some time to figure that one out, till I read a better explanation - that it allows for torque to flow down the line of least resistance. I could visualize that statement a lot better, to understand how one wheel in the air could ground a 4wd with a Torsen center diff in open mode.

I am not an engineer, but what helped too was the learnings from some years ago, from helping my son put together a Lego Technic car that had a gearbox and a differential.

Ironically, if you google torsen limited slip differential, the first hit is of a post that tells you it isn't a limited slip! I notice that the how stuff works is the second result, as I said, an excellent reference site.

PS: Just read the Chief engineer statement, and I retract my words, and I appreciate the learning from your post. I see why the limited word is indeed applicable, and the Pajero also probably has the same kind of limits on its center diff, before it reverts to allowing all the torque to flow to the spinning wheel. Thank you for the clarification!

[Samurai]

I hold a simple view. You have open differential and then fully locked differential (or no-differential), anything in between is limited slip differential. And torque is the minimum force required to overcome traction. I use that principle when I analyse the behavior my 4x4 vehicles offroad. BTW, I am an engineer from the days when they made us study other branches until 3rd year.

[Sawyer]

Getting to be like a dog worrying a bone here....
I am again muddled up. I suspect that some people call an open differential a Torsen differential. Correctly so, because they are sensitive to torque, and that is what drives their functioning.
On the other hand, an open diff, that is limited to an extent, would be called a LSD. Or even a Torsen LSD. Regardless of where it is placed, on the axles or in the center?
So that means the two words cannot be used interchangeably. Or so I think at this time!

[Samurai]

In an open differential, the wheel that that doesn't resist gets the torque. To quote you "that it allows for torque to flow down the line of least resistance". The torque sensitive LSD doesn't do that. It sends more torque to the wheel that resists.

[Sawyer]

Originally Posted by Samurai

In an open differential, the wheel that that doesn't resist gets the torque. To quote you "that it allows for torque to flow down the line of least resistance". The torque sensitive LSD doesn't do that. It sends more torque to the wheel that resists.

Yes, but since it does this by limiting the torque that would otherwise flow down that line to the spinning wheel, it does this in an indirect way, is my understanding. Beyond a point, it cannot cope, and it stops working, and all the torque reverts back to the spinning wheel. Till you lock it. Or so I think.
Now a question. Let's say you were told that a car has Torsen LSD/Torsen diff ( leave that difference if any aside for now) on its rear axle and you were told that another had a LSD on its rear axle, what difference would that signify to you about the two cars?

[Guna]

Here is an interesting video in the context of AWD with LSD in a Forester

YouTube - Subaru AWD vs. competitors