[Blooming Flower]

Originally Posted by purohitanuj

Once the rear wheels start to rotate, the torque at axles tends to go toward 0.

Hi Anuj,

Your assumptions are going towards ‘ideal’ situation from the real-life ‘practical’ ones. The ‘bending moment’ at the rear axle won't tend to zero in the situation you said or in any condition. Once you manage to roll the vehicle from a standstill you must accelerate (be it slower or faster) to reach a certain speed. Even to hold on the constant speed or keeping the vehicle in motion the engine has work continuously to overcome the 'total resistance' . The net resistance against rolling the vehicle is summation of vehicle inertia, drag (wind resistance) and the rolling resistance of the tires (plus some minor loss factors at each component down the drive-train level).

The torque at the axle will be lesser during a constant speed run than accelerating or braking, but never zero or close to it!

This parameters are very important to simulate an active or passive dyno-run for engine tuning. And the coefficients of those cumulative resistance parameters are obtained from a dedicated ‘coast-down’ test at OEM level. Google is your friend if you have interest in this!

Regards,
Debo

[keroo1099]

Originally Posted by Kosfactor

Given I have driven on sealed surfaces with steep gradients on 4L - I do not think there is any issue as long as your tire size is stock, your vehicle is not overloaded and you are easy on the A pedal

Sure it is not recommended to drive on sealed surfaces with 4WD engaged, but when you are climbing there is certainly different loads that each axle will experience, ideally the front wheels should slip and relieve the stress on the driveline when climbing.

+1 to this.

I have used 4L with front hubs disengaged a number of times going up Sigur Ghat in my MG410 in the 90's and never had an issue. What I did do was be gentle with the clutch, drive normally and found the car responded a lot better with the shorter gearing especially on the hairpins.

[purohitanuj]

Originally Posted by keroo1099

+1 to this.

I have used 4L with front hubs disengaged a number of times going up Sigur Ghat in my MG410 in the 90's and never had an issue. What I did do was be gentle with the clutch, drive normally and found the car responded a lot better with the shorter gearing especially on the hairpins.

This is exactly what I am targeting. The post for which you have responded talks in driving in 4L with front hubs locked.

My post actually allows one to drive in 4L with front hubs disconnected!

[motorguy]

@purohitanuj ..... We have been discussing doing this process using a Manual Transmission. Can anyone elaborate how do the driving in a Jimny equipped with Automatic transmission? Most important I guess is that the Torque Converter and other components should not get damaged.

[dhanushs]

Originally Posted by purohitanuj

..Once the rear wheels start to rotate, the torque at axles tends to go toward 0...

If torque is Zero whats pulling the vehicle up the hill? Please plug in a diagnostics tool and try to understand how torque works.

Originally Posted by purohitanuj

..
Here is a snippet from Jimny's Manual.
"Never operate your vehicle in “4H” or “4L” on dry pavement"

Well.. If what you have done (disconnecting the front hubs) was an expected behavior in stock vehicle conditions, then it would also be recorded in the manual.

You are just migrating from one problem to another.

Originally Posted by motorguy

@purohitanuj ..... We have been discussing doing this process using a Manual Transmission. Can anyone elaborate how do the driving in a Jimny equipped with Automatic transmission? Most important I guess is that the Torque Converter and other components should not get damaged.

AT or MT doesnt matter. For a given mass and acceleration the torque demand would be the same.

[purohitanuj]

Originally Posted by dhanushs

If torque is Zero whats pulling the vehicle up the hill? Please plug in a diagnostics tool and try to understand how torque works.

As I said, it tends to go toward zero. The momentum is also present. Its not like you put a moving car in neutral and it would stop instaneoulsy. If you ever drive a car with power and torque digital meter, try coasting or easing the throttle. The torque will go toward zero. The power(bhp) and torque work in different way. Then when you floor the pedal, torque will instaneoulsy (of what ever engine can produce at that rpm ; not the maximum torque the engine can produce) reach to its max but power wouldn't.
I think I need to plot a graph of stock torque vs 2wdL torque in MS Excel and share it here to make it more meaningful.

Originally Posted by dhanushs

Well.. If what you have done (disconnecting the front hubs) was an expected behavior in stock vehicle conditions, then it would also be recorded in the manual.

As this is a mod, off course it wouldn't be in the manual. Consider people are putting diff lockers to enhance the capabilities of the car; but is it documented in user manual? This mod is so simple, anyone who has driven free wheeling hubs would get the hang of it.

Originally Posted by dhanushs

You are just migrating from one problem to another.

Sorry but I dont get it. How does allowing one to steer freely in 4wd mitigates one problem to other? Please explain the context and I will be happy to post back.

[purohitanuj]

Originally Posted by motorguy

@purohitanuj ..... We have been discussing doing this process using a Manual Transmission. Can anyone elaborate how do the driving in a Jimny equipped with Automatic transmission? Most important I guess is that the Torque Converter and other components should not get damaged.

Mine is an AT and it works ( and more brilliantly in an MT). You just need to ease the throttle and not rip it out. As long as you drive with little caution and dont floor the accelerator, it should be just fine.

[dhanushs]

Originally Posted by purohitanuj

As I said, it tends to go toward zero. The momentum is also present....

Your 'mod' is all about about scenarios where the torque built by your regular transmission ratios is not sufficient and you need reduction of the TC. And now you say it tends to zero?

Originally Posted by purohitanuj

...
Sorry but I dont get it. How does allowing one to steer freely in 4wd mitigates one problem to other? Please explain the context and I will be happy to post back.

Steering does get affected, but not so much as to affect the dynamics at that speeds. The more pressing issue here is the windup on the drivetrain. Anyhow the other problem is your rear axle breaking.

[BlackPearl]

Originally Posted by purohitanuj

Consider the Sandakphu track which is now cemented, with steep gradients and very acute turns.
Hence, one cannot engage any of the 4WD modes available. And the grunt at initial pick of this 1.5L NA engine is way too less to get it moving from the steep slope.

Nice informative article purohitanuj, but please let me be the devil's advocate here as I do not agree to the use case mentioned above. I will mention the reasons in points -

1. The turns in Sandakphu especially for the last 3 Kilometers are so sharp and steep that even though they are cemented, the car will still slip the wheels on those turns, so chance of windup is negligible.

2. If the driver still has doubts, he/she can always take them in multiple attempts without putting too much pressure on the front axles.

3. It is very dangerous to suggest to take those turns in 2WD Low because if somehow you are not able to take the turn at one go and start slipping backwards towards the cliffs, I would want all my wheels to have power to take me out of that precarious situation, not just the rear wheels.

So while I agree with your points, I would never ever use 2WD Low in the mountains, because preventing transmission windup is the not the priority in those places.

[Geo_Ipe]

Extreme long shot solution for a very improbable situation of a problem! Theoretically, you're right. You're just highlighting the shortcomings of the Jimny - the inadequate engine. I use 2005 Scorpio 4*4 - which had 260 odd Nm of torque when new. I have done a fair share of off roading with other 4*4s like the Thar (new & old), Gurkha & the Pajero - none of these vehicles felt the need for a 2L mode. We have done extreme towing of broken down vehicles in sand as well as rocky terrain.

Jimny axles aren't probably as robust as the Thar ones - again highlighting another shortcoming of the Jimny. As you've mentioned, use the machine knowing its limits. Do all these modifications & DIYs at your own risk. If your use case demands more, get a more capable vehicle.

[Samurai]

Originally Posted by Geo_Ipe

Extreme long shot solution for a very improbable situation of a problem!

The last 3 kms of Sandakphu is really steep and curvy.

[Blooming Flower]

Originally Posted by BlackPearl

3. It is very dangerous to suggest to take those turns in 2WD Low because if somehow you are not able to take the turn at one go and start slipping backwards towards the cliffs, I would want all my wheels to have power to take me out of that precarious situation, not just the rear wheels.

Can't agree more with this point. I have been to several OTR destinations, but I can vouch I have never seen such a steep, gravelly and twisty road anywhere else other than the last 3-4 km climb to Sandakphu top. One has to witness this on his own to have a real feel.

Most 4x4 vehicles have longer turning radius and taking few turns at one go is next to impossible at some points. Jimny 5Dr is also infamous for its turning radius AFAIK.

Originally Posted by Geo_Ipe

If your use case demands more, get a more capable vehicle.

No better solution can be given than this.

At the same time, it's a mystery to me why no other high-end 4x4 vehicles with 3 differentials provide 4L with centre differential open except one (owned by moderator Blackpearl), I have found and mentioned in my initial post from the Thar CRDe review thread, which has been referred here.

Originally Posted by Blooming Flower

(Link) (The heartbeat of BlackPearl | Land Rover Defender 90 Review)

However, whether to use or not to use 2WD-L is nothing new, and has been discussed here a lot, a decade back by the veterans. I too suddenly found the thread while rummaging through the forum after this topic was featured on the home page. Giving the link for reference.

https://www.team-bhp.com/forum/4x4-t...isengaged.html (Using 4L for Engine Braking/Torque with FWH Disengaged)

[purohitanuj]

Originally Posted by dhanushs

Your 'mod' is all about about scenarios where the torque built by your regular transmission ratios is not sufficient and you need reduction of the TC. And now you say it tends to zero?

For your torque related query, please see this video and observe the shape of the leather/straps straps. I guess term "tending toward zero" needed more clarification to begin with. I hope the video clears my point. This is the closet I could find to explain what I meant.

https://youtube.com/watch?v=GxLHFPm8...J1dM1a_2lZVey4

Originally Posted by BlackPearl

Nice informative article purohitanuj, but please let me be the devil's advocate here as I do not agree to the use case mentioned above. I will mention the reasons in points -

1. The turns in Sandakphu especially for the last 3 Kilometers are so sharp and steep that even though they are cemented, the car will still slip the wheels on those turns, so chance of windup is negligible.

2. If the driver still has doubts, he/she can always take them in multiple attempts without putting too much pressure on the front axles.

3. It is very dangerous to suggest to take those turns in 2WD Low because if somehow you are not able to take the turn at one go and start slipping backwards towards the cliffs, I would want all my wheels to have power to take me out of that precarious situation, not just the rear wheels.

So while I agree with your points, I would never ever use 2WD Low in the mountains, because preventing transmission windup is the not the priority in those places.

I understand your point. But, many bolero local drivers have removed the fixed flange and replaced with FWH.
They simply unlock 1 wheel and drive. Intuitively, one would think they are driving in 3WD, but even freeing up one wheel will effectively make it 2WDL. And they do these roads all day; they would do this only if they see a huge benefit out of it.



As I said, only a driver who understands they 4WD system, and this technique , should use it.

[dhanushs]

Originally Posted by purohitanuj

For your torque related query, please see this video and observe the shape of the leather/straps straps. I guess term "tending toward zero" needed more clarification to begin with. I hope the video clears my point. This is the closet I could find to explain what I meant.
..

I'm sorry, the video doesnt clarify your point. Infact I'm a simple guy looking for simple answers. I was just asking the point of your mod, that 2H is not able to cater the torque, and you want more torque without the windup?

They simply unlock 1 wheel and drive. Intuitively, one would think they are driving in 3WD, but even freeing up one wheel will effectively make it 2WDL. And they do these roads all day; they would do this only if they see a huge benefit out of it

Just remember commercial segment vehicles are mostly designed for more than 3 times the rated values.

[purohitanuj]

Originally Posted by dhanushs

I'm sorry, the video doesnt clarify your point. Infact I'm a simple guy looking for simple answers. I was just asking the point of your mod, that 2H is not able to cater the torque, and you want more torque without the windup?

Just remember commercial segment vehicles are mostly designed for more than 3 times the rated values.

Point of the mod is beautifully written by you in this post:

https://www.team-bhp.com/forum/4x4-t...ml#post2989642 (Using 4L for Engine Braking/Torque with FWH Disengaged)