[Samurai]

The rotational torque delivered at the wheel is no more than what is required to rotate the wheels. Therefore, if you are in slippery ground and wheels are spinning, each wheel will get just a few Nm(s), just enough to spin them.

This is why super-torquey Thar CRDe and lowly XDP engined MM540s perform similarly in slushy terrains. Massive torque figures are great in tarmac and in terrains that offer much high traction, like rocks. Again, the moment the torque overcomes the traction offered by the ground, no more torque will be delivered.

In other words, if 50Nm of torque can overcome the traction offered by the ground, it doesn't matter whether your engine can deliver 100, 500 or 5000Nm. They will all deliver just above 50Nm and get the wheel spinning.

[SS-Traveller]

Originally Posted by Samurai

...the moment the torque overcomes the traction offered by the ground, no more torque will be delivered.

In other words, if 50Nm of torque can overcome the traction offered by the ground, it doesn't matter whether your engine can deliver 100, 500 or 5000Nm.

True.

In real life, when a huge amount of torque is being delivered to the wheels, and is being used to negotiate difficult but high-traction terrain (like a 40-degree-slope tarmac road with twists and turns), most vehicles with 4L (the Fortuner included) will wind up the transmission into a knot after a few km - only because the centre diff is locked. Apart from the Touareg...

Originally Posted by SS-Traveller

Low range selected, differentials not locked
Attachment 597077

...I am not aware of any other 4wd vehicle in India with 4L transfer case, which allows 4L operation without risking transmission windup.

@Samurai: Am I right in understanding that the GV also locks its centre diff when engaging 4L (i.e. you get 4LL)?

[suman]

So, for a layman like me, what do these mind-boggling numbers of the ToFu signify? How different would this be from, say, the performance of a 4wd Safari or Scorpio when going through (say) Pagal Nullah at its worst or Chang La or Zoji La or Marsimik La or any other really slushy terrain or water crossing in Ladakh?

Any first hand impressions or thoughts?

[Samurai]

Originally Posted by SS-Traveller

...I am not aware of any other 4wd vehicle in India with 4L transfer case, which allows 4L operation without risking transmission windup.

4WD with open center diff is only useful on tarmac, this is because if one wheel is slipping, all the remaining wheels lose power. Not really useful off the road. Therefore, it is rarely offered.

Originally Posted by SS-Traveller

@Samurai: Am I right in understanding that the GV also locks its centre diff when engaging 4L (i.e. you get 4LL)?

Yes, GV 4x4 system is exactly similar to Fortuner.

Originally Posted by suman

How different would this be from, say, the performance of a 4wd Safari or Scorpio when going through (say) Pagal Nullah at its worst or Chang La or Zoji La or Marsimik La or any other really slushy terrain or water crossing in Ladakh?

Between Fortuner, Safari and Scorpio, Safari is most likely to come out of the slush faster, thanks to rear LSD.

Still, you might see a lowly Gypsy out-perform all the above because of its lightness in the same slush.

[SS-Traveller]

Originally Posted by Samurai

...only useful on tarmac...

So true. The climb from South / North Pullu to Khardung La has enough twisties yet a tarmac road in some parts. With 4LL, one would worry a bit at times. Plus tyre wear goes up as the wheels scuff out the windup.

Originally Posted by suman

So, for a layman like me, what do these mind-boggling numbers of the ToFu signify?
Any first hand impressions or thoughts?

Originally Posted by Samurai

Between Fortuner, Safari and Scorpio, Safari is most likely to come out of the slush faster, thanks to rear LSD.
Still, you might see a lowly Gypsy out-perform all the above because of its lightness in the same slush.

Suman, between the Safari, Scorpio, GV, Gypsy and ToFu (I rather like that new name for the Fortuner, Suman ), I don't know about the one that will outperform the others; however, the one that will be beaten by the others is the one that you'll spend the most time cleaning up and restoring to sparkling state before and after crossing nullahs and passes. Going by that, the Gypsy, with it's least paint area to clean of all, is expected to outperform the others.

[suman]

Originally Posted by Samurai

Between Fortuner, Safari and Scorpio, Safari is most likely to come out of the slush faster, thanks to rear LSD.

Still, you might see a lowly Gypsy out-perform all the above because of its lightness in the same slush.

Yup, that's what I was thinking as well. So the mind-boggling numbers may not really be relevant in a real world situation.

Originally Posted by SS-Traveller

Suman, between the Safari, Scorpio, GV, Gypsy and ToFu (I rather like that new name for the Fortuner, Suman ),

Thanks Doc .

[nilanjanray]

Ok, thanks for the laugh w.r.t. Tofu, folks. But do I detect a tiny sarcastic note? I wonder why, given that this is a Fortuner thread.

Anyway, I have a few questions for folks well versed with 4WD driving and mountain driving, because the last few posts seem to have the same theme: all that torque with a Torsen setup is useless in real life offroading scenarios.

1. Why would someone ever use 4LL on tarmac or high traction terrain for an extended period, and risk transmission windup? How many such trails - worth traveling on i.e. leading to a good destination (instead of just tacking a trail to see whether your vehicle can handle it) exist in India? I haven't been to Ladakh, so I am curious to know. Are these roads so steep that one can't tackle them on 4H with 350 NM torque and a decent torque/weight ratio?

2. Wouldn't power/weight ratio play a role in slushy terrain, especially in 4HL mode - with respect to added momentum ? Why would one use 4LL in slushy terrain - the extra torque would ensure wheel spin.

3. The Arjun, while heavier than the T-90, has a lower weight/sq inch figure than the T-90 - this, along with its more powerful engine, helps in the sand. Is it absolute weight that matters, or weight per square inch of surface area? To what extent to larger tyres (more surface area especially when deflated), and power/weight and torque/weight ratios impact drivability through slush or snow? Given similar sized tyres and say similar torque and power to weight ratios (if that were possible), and ignoring wheel base size, would a lighter Jeep or Gypsy outperform a heavier Thar, say? Let's keep driver skill, 4WD system etc. constant.

4. To what extent can handbrake negate free rear wheel spinning, and allow Torsen setup to deliver adequate torque to the wheel with traction?

5. Why have high torque + good low range transfer case ratios on SUVs at all - apart from the low speed crawling angle?

@ SS-Traveller: "the one that will be beaten by the others is the one that you'll spend the most time cleaning up and restoring to sparkling state before and after crossing nullahs and passes." - what makes you think that someone who takes their SUV to difficult terrains is bothered about vehicle look in the middle of such a journey? Besides, who will do a Manali-Leh circuit or cross-country drive with offroading thrown in - with family - in a Gypsy or a Jeep?

[tsk1979]

Originally Posted by nilanjanray

Ok, thanks for the laugh w.r.t. Tofu, folks. But do I detect a tiny sarcastic note? I wonder why, given that this is a Fortuner thread.

Anyway, I have a few questions for folks well versed with 4WD driving and mountain driving, because the last few posts seem to have the same theme: all that torque with a Torsen setup is useless in real life offroading scenarios.

1. Why would someone ever use 4LL on tarmac or high traction terrain for an extended period, and risk transmission windup? How many such trails - worth traveling on i.e. leading to a good destination (instead of just tacking a trail to see whether your vehicle can handle it) exist in India? I haven't been to Ladakh, so I am curious to know. Are these roads so steep that one can't tackle them on 4H with 350 NM torque and a decent torque/weight ratio?

Yes, there are certain trails which go somewhere and require 4L.
I just have one example on video

Tanveer's 4x4 on the Agham - Shyok route. - YouTube

The fortuner can also do this trail provided you lock the center diff. On 4H you will be so fast that the vehicle can get damaged

2. Wouldn't power/weight ratio play a role in slushy terrain, especially in 4HL mode - with respect to added momentum ? Why would one use 4LL in slushy terrain - the extra torque would ensure wheel spin.

Depends on slush, sometimes in thick mud its so sticky that you cannot even spin wheels in 1H. The engine will stall. So if you get stuck, you need to shift to 4L and then gently rock back and forth. Sand is another such place.
That said, slush is best done in 3rd or 2nd low at some speed.

3. The Arjun, while heavier than the T-90, has a lower weight/sq inch figure than the T-90 - this, along with its more powerful engine, helps in the sand. Is it absolute weight that matters, or weight per square inch of surface area? To what extent to larger tyres (more surface area especially when deflated), and power/weight and torque/weight ratios impact drivability through slush or snow? Given similar sized tyres and say similar torque and power to weight ratios (if that were possible), and ignoring wheel base size, would a lighter Jeep or Gypsy outperform a heavier Thar, say? Let's keep driver skill, 4WD system etc. constant.

Weight/square inch matters. So even with skinny tires the 980kgs gypsy will outperform our 2 ton + behemoths, unless you have really really wide tires.
Other than that the overhangs help.
In snow, your tread deepness helps. HT tires are horrible on snow.

4. To what extent can handbrake negate free rear wheel spinning, and allow Torsen setup to deliver adequate torque to the wheel with traction?

LSD is useful only just a little bit. If you really want to get out, diff has to be locked if you are really stuck.
That said crossing a slushy path at apeed, LSD equipped vehicles do it better than open diff vehicles. Have experienced this first had at 4 guna 4

5. Why have high torque + good low range transfer case ratios on SUVs at all - apart from the low speed crawling angle?

Steep inclines, rocky terrain(speed control necessary). Also sometimes high gear cannot deliver enough torque without clutch burning.

@ SS-Traveller: "the one that will be beaten by the others is the one that you'll spend the most time cleaning up and restoring to sparkling state before and after crossing nullahs and passes." - what makes you think that someone who takes their SUV to difficult terrains is bothered about vehicle look in the middle of such a journey? Besides, who will do a Manali-Leh circuit or cross-country drive with offroading thrown in - with family - in a Gypsy or a Jeep?

I know a few who actually took their family to Leh in a jeep, and that too a auction bought and restored jeep.

[nilanjanray]

Originally Posted by tsk1979

Yes, there are certain trails which go somewhere and require 4L.
I just have one example on video...

The fortuner can also do this trail provided you lock the center diff. On 4H you will be so fast that the vehicle can get damaged


Depends on slush, sometimes in thick mud its so sticky that you cannot even spin wheels in 1H. The engine will stall. So if you get stuck, you need to shift to 4L and then gently rock back and forth. Sand is another such place.
That said, slush is best done in 3rd or 2nd low at some speed.


I know a few who actually took their family to Leh in a jeep, and that too a auction bought and restored jeep.

Thanks Tanveer.

Yes, given the rocks, a slow crawl is required. Where was that track leading to? And did the Swift try to climb up?

I guess I was inadvertently thinking of 1st 4LL when I asked why would one use 4LL in slush. Like you, the instructors in the 4WD bootcamp recommended 2nd or 3rd 4LL through slush - and when I did the circuit multiple times, I found 2nd or 3rd 4LL to be pretty effective through deep slush at decent speeds.

Kudos to those brave folks who did the Leh circuit in a jeep. Their choice. But I wouldn't want to do that, because comfort and protection from dust and fumes are of priority to me when I travel with family - and especially since I have a toddler at home.

[mxx]

Originally Posted by SS-Traveller

True.

In real life, when a huge amount of torque is being delivered to the wheels, and is being used to negotiate difficult but high-traction terrain (like a 40-degree-slope tarmac road with twists and turns), most vehicles with 4L (the Fortuner included) will wind up the transmission into a knot after a few km - only because the centre diff is locked. Apart from the Touareg...

...I am not aware of any other 4wd vehicle in India with 4L transfer case, which allows 4L operation without risking transmission windup.

Ot but since asked,
Merc GWagon
Discovery 4
Range Rover Vogue

[Manuuj]

Dear all,

This is an interesting read on 4 wheeling and a good explanation on transmission windup, its causes and cures.

Sharing with you guys in the hope that im not flouting any rules.

4WD Driving Skills: A Manual for on ... - Google Books

[Aroy]

Originally Posted by Manuuj

Dear all,

This is an interesting read on 4 wheeling and a good explanation on transmission windup, its causes and cures.

Sharing with you guys in the hope that im not flouting any rules.

4WD Driving Skills: A Manual for on ... - Google Books

Quite an informative book. Pity only 24 pages are available for review. Will try to get this book some times.

[nilanjanray]

I bought this one recently: pretty good.

Books - 4WD Handbook @ ExplorOz Shop

[redrage]

Planning to pick up the fortuner i.e current gen. Any advice on whether it would be worthwhile to wait for the new version?
P.S Interiors don't really care much. Test drove the present gen and found it ok.

Any other things i need to watch out?

[dkaile]

Originally Posted by redrage

Planning to pick up the fortuner i.e current gen. Any advice on whether it would be worthwhile to wait for the new version?
P.S Interiors don't really care much. Test drove the present gen and found it ok.

Any other things i need to watch out?

Have a look here - http://www.team-bhp.com/forum/suvs-m...-fortuner.html Its been discussed and polled in detail. Otherwise the refreshed look ain't bad either. Go for the current one for Classic looks and heavy discount (if possible).