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Old 26th August 2009, 14:38   #16
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Originally Posted by Ym-enjn View Post

Is this not the 4x4 high in our jeeps? With the front and rear shaft engaged and open differentials?

In the Jeep there would be differentials on both axles, to accomodate different rates of wheel rotation. The center differential is missing, this is what accomodates different rates of axle rotation. With a center diff, if you leave it open, you can run 4wd on roads where the tyre has good road adhesion as well, without stressing the driveline. Because the Jeep does not have the center diff, you do not want to run it in 4wd mode on tarmac, but only in places where the tyres can release the pressure on the driveline on turns by losing road traction first.

Why a star * there? Does that means that it has got only one differential in the center and no more at rear and front axle?

The center diff is in addition to the other two. Unless one of the axles has independent shafts driving each of the wheels it carries, the car would then have three differentials.



Is this mode basically locking the diffrentials and not the shafts, as that is already connected?

Sorry if I sound silly...
Nothing silly about the questions, the inconsistent jargon that the industry uses for all this stuff confuses the hell out of most people. I am sure I still haven't got it all sorted out yet!
PS: More importantly, Fortuner owners need to get all of this sorted out before they start driving their new cars, because they can wreck them very quickly by running them in 4HL mode on the highway.

Last edited by Sawyer : 26th August 2009 at 14:49.
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Old 26th August 2009, 14:46   #17
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N mode - All wheels will be disengaged from the transfer case. Useful for towing only, never engage this lightly. If the vehicle is towed by traffic cops in normal fashion (lifting one side), your vehicle will be severely damaged.
Well, read all these while waiting impatiently for the booked Fortuner to come, and I feel humiliated that I thought of myself as knowledgeable somebody in 4x4 tech uptill now as the former owner of a Pajero, a Prado and a Series 100 Land Cruiser!

Well, would you be so kind and enlighten me more on the "N" mode? Did you mean that if the vehicle is in "N" while being towed by the cops, or in a similar fashion, it would be damaging? Then in what position should be the car left?

Last edited by Yeldo : 26th August 2009 at 14:47.
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Old 26th August 2009, 14:49   #18
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Originally Posted by Ym-enjn View Post
Right at the time I though I understand 4x4 completely.
That's a long journey, trust me. Everytime you think you understand, your vehicle will behave differently and confuse you entirely.

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Originally Posted by Ym-enjn View Post
Is this not the 4x4 high in our jeeps? With the front and rear shaft engaged and open differentials?
No, our Jeeps don't have center diff in addition.

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Originally Posted by Ym-enjn View Post
Why a star * there? Does that means that it has got only one differential in the center and no more at rear and front axle?
Star was an indication of footnote, which was provided later. Fulltime 4WD vehicles always have front, rear and center diff.

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Originally Posted by Ym-enjn View Post
Is this mode basically locking the diffrentials and not the shafts, as that is already connected?
When you lock the center differential, the front and rear drive shaft (not axles) spin together like a single shaft. Now the slip has to be provided by the road. If driven on tarmac, there will be no slip and cause driveline windup. This is the case in Jeeps in 4WD mode.

Coming back to the topic. I am still not too sure what kind of center LSD is used in Fortuner. The south african site of Fortuner says torque sensing, so I thought it was same as GV. But Tini says otherwise...

Can we atleast agree Fortuner has open diffs in front and rear? I don't see any mention of rear LSD.
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Old 26th August 2009, 15:01   #19
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Can we atleast agree Fortuner has open diffs in front and rear? I don't see any mention of rear LSD.
Even with a LSD, they would still be termed open diffs, I believe. I haven't picked up any reference to a LSD on the rear axle in the materials for the Fortuner. As far as I know the one Indian car that has lockable front and rear diffs is the Gurkha. I haven't come across any other. Are there any others?
@Yeldo, it is a mystery to me how so many people that run cars like the ones that you mention, not knowing these issues, manage to not wreck their cars! That was my first reaction when I got familiar with 4wd. I have seen Pajeros run by lots of people that haven't a clue about this - perhaps they do ok because they just leave the little lever alone, I don't know. And as far as the N on it is concerned, I have never had reason to think about it, and have never used it. What would happen if the car was towed with the big shift in N, and the little shift not in N, I am still to learn. Or what happens if the big shift is in 1st and the little shift is in N for that matter. I suspect that if either of the two is in N, its ok for towing, but that is a guess.

Last edited by Sawyer : 26th August 2009 at 15:03.
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Old 26th August 2009, 16:10   #20
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Originally Posted by Yeldo View Post
Well, read all these while waiting impatiently for the booked Fortuner to come, and I feel humiliated that I thought of myself as knowledgeable somebody in 4x4 tech uptill now as the former owner of a Pajero, a Prado and a Series 100 Land Cruiser!
Don't they all have 2WD mode, that negates the need for N mode.

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Well, would you be so kind and enlighten me more on the "N" mode? Did you mean that if the vehicle is in "N" while being towed by the cops, or in a similar fashion, it would be damaging? Then in what position should be the car left?
If they tow in your absence, then there is nobody to shift it to N.

I used to have better resolution images, but I can't find it now. But this should give you some idea.

Center Differential and LSD in SUVs-gvmodes.jpg

Until proven otherwise I am inclined to think that Fortuner 4WD works exactly like this.

Last edited by Samurai : 26th August 2009 at 16:13.
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Old 26th August 2009, 17:16   #21
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^^ Thanks Samurai and Sawyer for explanation. I have few questions in mind which I will post later.
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Old 26th August 2009, 17:37   #22
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This might be a stupid query, but I wanted to know that if the fortuner and a lot of other vehicles can be all time 4WD then why do they recommend not to engage 4WD on tarmac roads / hard surfaces in the Safari Dicor.
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Old 26th August 2009, 17:39   #23
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The thought that comes to mind is does all this 4wd stuff to keep in mind - that is important to know - attract potential Fortuner buyers, or does it turn them off?! The large majority will remain blissfully unaware, I guess! And since the Fortuner starts with the 4H position by default, leaving the stick undisturbed will still serve them well enough on a permanent basis, with no harm to the car.
@Sidcruise - because the Safari does not have a center differential. Like the Jeeps/Gypsies. And I am guessing the Scorpios too.

Last edited by Sawyer : 26th August 2009 at 17:41.
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Old 26th August 2009, 18:38   #24
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Originally Posted by Samurai View Post
Tini, I got that from here: Fortuner
See this page from the same website:

Toyota Vehicle Specifications

The rear differential and center differential can be locked. The rear has Torque sensing LSD not the central diff.

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Originally Posted by Samurai View Post

Can we atleast agree Fortuner has open diffs in front and rear? I don't see any mention of rear LSD.

Actually we can't agree . It has open front Diff. The rear diff is Torque Sensing LSD with Lock. i.e. Normally it is in Limited slip mode but it can be driven in fully locked mode with equal distribution to left and right wheel. The front is open diffs. Center is open with a lock. There is no torque sensing auto 4WD in the center. It is either open or locked.



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@Sidcruise - because the Safari does not have a center differential. Like the Jeeps/Gypsies. And I am guessing the Scorpios too.
Scorpio is part-time too. No Center Diff.

Last edited by 4x4addict : 26th August 2009 at 18:40.
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Old 26th August 2009, 19:14   #25
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@4x4addict - I am not so sure, and here is my reading of the same spec and reconciling that with what I know.
I think the reference to the torque sensing differential with a lock refers to the center diff.
And I will stick out my head on a limb and say that I think that the spec on the site is wrong in saying center and rear differential locks. If I am wrong, I am willing to accept that if someone sees the car and finds out how to lock the rear differential on it!
Waiting to be shot down!!
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Old 26th August 2009, 19:30   #26
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Originally Posted by 4x4addict View Post
Actually we can't agree . It has open front Diff. The rear diff is Torque Sensing LSD with Lock. i.e. Normally it is in Limited slip mode but it can be driven in fully locked mode with equal distribution to left and right wheel. The front is open diffs. Center is open with a lock. There is no torque sensing auto 4WD in the center. It is either open or locked.
Nooo, that doesn't make sense. There is no point in having LSD on rear diff when center diff is open. In that case, if one front wheel looses traction, then the entire vehicle will lose all torque.

Remember, torque is the least amount of force required to make the wheel turn. If one front wheel spins freely due to lack of traction, no torque will be delivered to front axle because of open diff. If the center is also open, no torque will be delivered to the rear axle either. You are stuck royally. This is no different than 2WD.

If there is LSD, it has to be on center diff first. I have to agree with Sawyer about the data on that web, looks like they cut-n-pasted from the LC page.

Last edited by Samurai : 26th August 2009 at 20:05.
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Old 26th August 2009, 20:00   #27
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You guys raise a valid point.

Sawyer, the specs maybe vague, but I suspect Driving in Center diff locked mode also locks the rear diff. So there may not need to be a separate button to engage the rear diff lock.

I'll check with my neighborhood Toyota Salesman in chennai and update you guys. Just kidding.. I will have to explain to him what the Kutty (small) lever is for first. I am sure they have already coined some local lingo for the 4WD Lever like "Power-Lever", or something like that..
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Old 26th August 2009, 20:14   #28
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I am sure they have already coined some local lingo for the 4WD Lever like "Power-Lever", or something like that..
Thank you for making my day!
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Old 26th August 2009, 20:19   #29
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Sawyer, the specs maybe vague, but I suspect Driving in Center diff locked mode also locks the rear diff. So there may not need to be a separate button to engage the rear diff lock.
I have to again disagree... Think again Tini, engaging center and rear diff lock is really serious business, needed only in very hardcore offroad situation. This is like engaging rear diff lock in Gurkha. It can destroy the driveline (transmission windup and axle windup) within few meters of hard tarmac just by moving the lever to 4H by mistake. Why would Toyota give it in a SUV like this?

If rear diff is locked, you just have to turn in place on hard ground (just one wheel turns) to damage the axle.
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Old 26th August 2009, 20:44   #30
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I think that the Fortuner is very much like the GV, from all I read, in terms of offered 4wd features. How exactly the open center diff functions in the two cars may differ in engineering details, but the outcome would be the same. For example, the one in the Pajero, when open, uses a VCU - viscous coupling unit to allow for moving torque across the two driveshaft/axles. The Fortuner probably uses the Torsen LSD, a purely mechanical device, to achieve the same effect. GV- I don't know. Regardless, not much difference in what they offer as an outcome. And of course, both can be locked.
In addition to the above, and 2wd, the Pajero also has a mechanical limited slip differential on the rear axle, that is always in use. Sort of a halfway house between a fully open differential, and one that is locked.
I am not sure what kind of a differential the GV or the Fortuner has on the rear. It could be open, limited slip, or lockable. I know that the GV does not have it lockable, but there seems to be some confusion about the Fortuner.
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