[purohitanuj]

Jimny 2WD Low Mode Mod

How to drive Jimny in 2L ( 2 wheel drive ) in Low mode of transfer case?

1. Why do it?

As Jimny has a part time 4WD, you cannot use on high friction roads which require steering inputs. 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.

Another great topic to see the reason and other technical bits is here:
https://www.team-bhp.com/forum/test-...ml#post5764092 (Review: 1st-gen Mahindra Thar (2011 - 2019))

Transfer Case to the rescue!

Imagine a world where you can put Jimny in 4L and disconnect the front wheels. Now you can steer as much as you want without thinking of and windup in gears. This would have been possible if Jimny had freewheeling hubs; which it does not.

So let me explain the 4WD system of Jimny a bit.
There is a transfer case which has 3 options ( actually it has 4, but lets focus on 3)
1. 2H
2. 4H
3. 4L

In 2H, the TCase output shaft and input shafts are connected in 1:1 ratio ( for simplicity here but in real its 1:1.32).

The Tcase has 1 input shaft and 2 output shaft. 1 of the output shaft goes to the rear differential and 1 to the front.
The rear output shaft is always connected, but for the front shaft, there is a mechanical mechanism which slots the front output shaft into the drivetrain.

This happens when you pull the lever to 4H; i.e. the front shaft from transfer case to the front differential engages.

This mechanism helps in maximising efficiency as in 2H, your engine is not rotating unwanted components.

Ok which this done, the front axles in the shafts are also rotated which are connected to both ends via the differential; but these are not connected to the tyres yet.

Why So? Consider if they had been connected, then in 2H, they tyres would have been rotating these shafts and hence again decreasing the efficiency and also more wear and tear.
Thus there is a way to attach the tyres with the axles.

This is where the hubs come into play. There are many ways to lock the wheels to the axles like electrically actuation; Jimny has Vacuum assisted hubs.
In this technique, the engine produces vacuum which literally sucks a diaphragm and move the teeth of the wheel hub closer to the axle teeth and interlocks them.

As this method is dependent on engine vacuum, which is a function of atmospheric pressure, hence you will find Jimny struggle to lock its hubs in high altitude region. You will need to rev the engine to lock the hubs in those regions. A blinking 4WD light in the dashboard lets the driver know that the hubs are not yet locked.

Now coming to the main topic, we can get way to disconnect the front hub locking mechanism, we can make sure that the front wheels do not lock to the powered axles.

This is were the crux of the above mod comes in. There are two solenoids which are responsible to enable / disable the flow of engine vacuum. If we can cut the power to these, the Jimny would effectively be in 2WD always.
This is like keeping the freewheeling hubs as in 4x2 mode with 4wd applied.

How to we do it?
Its simple, just pull out the fuse 24 from the front fuse box in the engine bay.

This is the fuse.


After you disconnect the fuse and start the car, the car will tell you that the ESP is offline and a check engine and check transmission light will be on. This will go away if you replace the fuse and drive for 30-40 minutes in 3-4 engine cycles.

This video shows me driving in 2H on tarmac road with 30km/hr at 3000 RPM and then in 4L with fuse removed ( effectively in 2WDL ) on same tarmac with 15km/hr at 3000 RPM. The steering is as it is in 2H and I can use and turn it anyway.

This is the video:

https://youtu.be/cjser4WunYY

After putting the fuse back, I had the engine check light and transmission error light lit up on the dashboard. All other errors were gone. The car drove normally, the 4x4 system worked perfectly, and the Aircon also worked fine.

After driving around the car for 40-50 minutes and with cycling engine on off 3-4 times, the dashboard MILs also went away.
I then hooked up the ODB scanner to see if there are any pending code, which as expected were 0.


I then go ahead to see history of codes, which also as expected showed a 4WD error.



I then cleared the codes and it also went away from history.


Hence, I think this is a good way to engage 2WD Low in cases where its applicable; and reverts back Jimny to its default driving conditions.

Some of the examples where one would want to do it:
1. Hatu peak in summers.
2. Sandakphu
3. Towing a vehicle on roads.

This mod should work on current gen Thar as it has electronic locking front hubs and a mechanically locking Tcase.
It will not work in (some ?) Gurkha as it comes with always locked front wheels ( hence the 4x2 and 4x4 high efficiency is almost same)

Fulltime 4wd and AWD are different and not be confused here.

Hope I was able to explain this enough. Bye cheers!.

Disclaimer: Use it at your own risk and if you understand what is happening and when required for short time.

[Shreyans_Jain]

Originally Posted by purohitanuj

Jimny 2WD Low Mode Mod

This is like keeping the freewheeling hubs as in 4x2 mode with 4wd applied.


Some of the examples where one would want to do it:
1. Hatu peak in summers.
2. Sandakphu
3. Towing a vehicle on roads.

Very clever. Thanks for sharing. A nifty solution for Jimny owners when they are out in the wilderness.

Speaking of the specific examples you have mentioned, I firmly believe a simple EV with good ground clearance will be even better for such steep and narrow trails. Last November, I took my Nexon EV LR to the very top of Hatu Peak, and the car climbed very easily without skipping a beat. I was literally mobbed by local taxiwallas at the temple, so surprised and curious they were about a green plate Nexon making it all the way up there. The year before, I had attempted the same with my Compass, which absolutely struggled and I called it quits half way. EV torque is the perfect solution for steep climbs. No revs, no clutch, no complications and no noise and smoke.

[Blooming Flower]

Originally Posted by purohitanuj

Jimny 2WD Low Mode Mod

How to drive Jimny in 2L ( 2 wheel drive ) in Low mode of transfer case?

Another great topic to see the reason and other technical bits is here:
https://www.team-bhp.com/forum/test-...ml#post5764092 (Review: 1st-gen Mahindra Thar (2011 - 2019))

Disclaimer: Use it at your own risk and if you understand what is happening and when required for short time.

With reference to my post quoted here, I wish to re-iterate the following things which may be considered as a statutory warning before trying to push the car in 2WD-low mode.

First of all, theoretically almost doubling of the twist force exerted on the rear axle is real what-so-ever be the way to implement 2L. This is not easy to visualize unless one knows the mechanisms of how 4WD works. Visualization with bare eyes is only possible if the FOS (factor of safety) or the particular ‘designed failure mode’ is exceeded leading to twisting of the rear axle as shown below. Otherwise, if some strain gauges are pasted on the axle and a data logger is used to record the objective values of strain under 4L and 2L situation-- that will substantiate what I am trying to purport here, even within the designed FOS limit.

However, let’s delve deeper into some hypothetical situations. Many times we have seen the overloaded commercial vehicles are stalled on the road due to ‘broken axle’. Now focus on the word ‘broken’.

What is the mechanics of axle breaking?

Axle can fail in two ways.

1. Buckling under excessive vertical load.
2. Twisting of the axle to roll the wheel.

Now buckling can happen in two ways. Let’s consider-- two similar pick-up trucks carrying load on their bed, 1 ton and 2 ton respectively, and the manufacturer recommended max. load is 0.8 ton. On paper, the chances of breaking the axle due to vertical load is greater for the second one. But practically it can happen to the 1T load carrying truck also. Imagine the 1T truck was plying on a road full of craters and potholes at a moderately high speed. There may be a situation when the impact load on the axle due to these crater/ potholes can exceed 2T value leading to ‘early’ failure of the axle.

To visualize the situation, imagine a 5 kg iron ball kept on a wooden table and the same ball being dropped on the table from a height.

If axle is rated for 0.8T vertical load its FOS is designed to take that max. impact load arising (which is way more than 0.8T) from the worst possible driving cycle. But again, this has an upper limit.

Now, note the word ‘early’ failure. Why this is?

Buckling can happen through static load, impact load, and also due to onset of ‘creep’. Creep can be defined as the failure of a load-carrying member subject to constant load for a prolonged time. This is the gradual failure under the same load case operation. That is why a truck can be run overloaded for a long time and suddenly one fine day, the axle breaks apart.

Let's understand the twist part. The twist force on the axle to roll/ move the wheel is equal to the vertical load multiplied by the frictional coefficient between the tire and road surface. But this is an over-simplification and ideal situation similar to solving a simple physics problem from childhood. The reality is different. The ‘ideal’ from the physics is replaced by the ‘practicals’ of the engineering to solve real-life problems. There exist several other parameters contributing to the net twist force on the axle. For example, consider the pulley problem of classical mechanics. We always neglected the mass of the string to solve the problem. But in ‘engineering’ this is important and must be considered. Just for the sake of easier understanding I chose to simplify.

So if someone tries to emulate 2L mode in their part-time 4WD vehicles do at your own risk only if you know the limits of your vehicle very well. If one fails to do the mental math based on the situational use case things can pretty much go on the wrong side.

For my use case, the following statement is practically valid and I shall use this mode for very short time to roll the vehicle in motion in the given situation.

Originally Posted by Blooming Flower

If you look at the rear axle, the net twisting force exerted on it in either case (2H and 2L) will be exactly equal for moving the vehicle up. Rather, in 2H there remains a high probability of frying up the clutch.

Anyways, to dilute the seriousness of the aforementioned facts let’s look at these.

Hypothetically, there can be more use cases of 2WD-L mode apart from what I explained in my previous post in the other thread.

1. The driver of an open-top jeep used in election campaign can slot to 1st gear in this mode and give his feet much needed rest doing no ABC. The same is applicable for the jeeps used in tableau/ procession of Ganapati or other idols immersion.

2. I know many 4WD owners who never used 4WD mode. They can use this mode on normal road to splash lubricate the front differential.

Yes, pun intended!

Last but not the least, 2WD-L can provide you more control while descending a downhill road with full traction without worrying about axle twist and TM windup.

Having said that, I repeat, there exists ample scope of breaking the axle if the math goes wrong!

[Rehaan]

Enabling 2WD Low Mode (2WDL) for the Maruti Jimny: A simple modification

Posts split into a new thread from the Jimny Review thread.

[svsantosh]

Originally Posted by purohitanuj

1. Why do it?
As Jimny has a part time 4WD, you cannot use on high friction roads which require steering inputs.

If Torque-Steer is the only thing you are trying to overcome, how is a 100% torque to a rear wheel 2WD and the slender prop shaft going to help?

[purohitanuj]

Originally Posted by svsantosh

If Torque-Steer is the only thing you are trying to overcome, how is a 100% torque to a rear wheel 2WD and the slender prop shaft going to help?

My post has nothing to do with torque steer.
Consider what happens in RWD at all times? 100% torque to rear wheels. Hence, I would request you to please elaborate your question.

[purohitanuj]

Why you cannot and should not use Part Time 4WD on paved roads ( ground with good friction)?

Quick KT on this is below:

When you steer any car, such as making a right turn, the wheels on the left side must cover a longer distance than the wheels on the right side. This discrepancy arises due to the varying turning radii of the left and right wheels. Consequently, the left wheels need to rotate faster than the right wheels. This difference in rotational speed (RPM) between the left and right wheels (similarly observed between front and rear wheels) is managed by a component called the differential.

Now, let’s delve into how this applies specifically to a part-time 4WD vehicle, like the Jimny:

1.Differential Locking:
When you engage 4WD in your Jimny, the front and rear differentials are locked together. In this context, “locking” means that the front and rear diffs are synchronized, but it’s essential to note that this isn’t the same as having mechanical locking differentials.
Essentially, all the wheels (at least three of them!) wants to rotate at the same RPM. This synchronization ensures that power is distributed evenly to all wheels.

2.Natural Opposition to Turning:
Due to this locked (synchronized) differentials, the car naturally resists turning. If you attempt to force a turn, the car will comply, but some wheels will skid on the ground to compensate for the varying distances they need to cover.
On soft terrains like sand, snow, or dirt roads, wheel skidding is possible without significant issues.

3.The Challenge on Hard Surfaces:
However, on regular roads or any hard surface with good friction between the ground and the tires, a problem arises. The wheels are not allowed to skid, but they have to. Hence there will be great stress on the drivetrain components mostly leading to winding of the diffs or transmission.
Consequently, the car tends to go straight and avoids turning effectively.
Imagine a toy car with its left and right wheels joined together. To make it turn, the wheels must skid.

4.Driving Considerations:
For part-time 4WD vehicles (like the Jimny), driving is recommended only on surfaces that allow the tires to skid easily.
If the friction between the tires and the road surface is strong (as on regular roads), avoid using 4WD while turning. The tension in the mechanism during turns can act as a braking effect, potentially damaging the differential.

[Samurai]

Originally Posted by Blooming Flower

First of all, theoretically almost doubling of the twist force exerted on the rear axle is real what-so-ever be the way to implement 2L.

That's the first thing I thought about when I saw the title. Then I clicked on the thread and found it is already highlighted by you.

[Rocketscience]

Originally Posted by Shreyans_Jain

The year before, I had attempted the same with my Compass, which absolutely struggled and I called it quits half way. EV torque is the perfect solution for steep climbs. No revs, no clutch, no complications and no noise and smoke.

While an EV might do better than ICE cars there (I have not driven one in that exact road), but your Compass struggling there and struggling so much that you had to abandon it half way seems highly surprising to me, for me having went there on much lesser cars like Swift and Baleno and majority of Taxis there being the humble Alto 800, climbing every day with ease day in and day out. That is road is somewhat steep yes, but it is not extraordinary in Himachal to find similar roads, my in laws are from there and their native village has access from very similar single steep roads and they make the climb in their Baleno and earlier in Alto with ease.
It is not the kind of road which even requires any kind of 4x4, torque monster or any extra ordinary car is the impression I have for the road.

[dhanushs]

@OP - Your problem of not able to engage 4L in tarmac/grippy surfaces is very relvant. There is a bit of windup caused and continuous running will wear out your mechanicals.

However, manufactuers do account for the transfercase windup to an extent and your tyre will be the fuse. However, by disconnecting your hubs, you risk breaking your rear axle by not allowing the front wheels to carry some of the torque. I know Jimny owners who have broken rear axle just by installing lockers and doing some towing.

So, if you are not easy on the pedal you do risk breaking your rear axle.

[purohitanuj]

Originally Posted by dhanushs

@OP - Your problem of not able to engage 4L in tarmac/grippy surfaces is very relvant. There is a bit of windup caused and continuous running will wear out your mechanicals.

However, manufactuers do account for the transfercase windup to an extent and your tyre will be the fuse. However, by disconnecting your hubs, you risk breaking your rear axle by not allowing the front wheels to carry some of the torque. I know Jimny owners who have broken rear axle just by installing lockers and doing some towing.

So, if you are not easy on the pedal you do risk breaking your rear axle.

Yes, I do understand the risk and assume anyone well versed with 4WD would know how much to push. Once the rear wheels start to rotate, the torque at axles tends to go toward 0. Only if your rear wheels are dead stuck, and then you shift into 2L, and rev the engine till 4K and dump the clutch would mean you are very close to twisting or breaking the axles. Climbing steep gradients slowly, gradually and with calculated input to throttle would not post much issue.

Also many Jimny owners are already driving in 4L with in high altitude regions with the 4WD light blinking i.e. hubs are not locked and effectively it's in 2WD L. They have little clue that they need to rev the engine and keep it revving and then shift into 4H to make sure the hubs get locked.

[Shreyans_Jain]

Originally Posted by Rocketscience

While an EV might do better than ICE cars there (I have not driven one in that exact road), but your Compass struggling there and struggling so much that you had to abandon it half way seems highly surprising to me, for me having went there on much lesser cars like Swift and Baleno and majority of Taxis there being the humble Alto 800, climbing every day with ease day in and day out. That is road is somewhat steep yes, but it is not extraordinary in Himachal to find similar roads, my in laws are from there and their native village has access from very similar single steep roads and they make the climb in their Baleno and earlier in Alto with ease.
It is not the kind of road which even requires any kind of 4x4, torque monster or any extra ordinary car is the impression I have for the road.

Compass (diesel manual 4x2) struggled because its first gear is simply too tall for such trails. Keeping any sort of momentum meant the car was going too fast. The width of the car and the large turning circle were also troublesome. There were many instances where three point turns were required, and the car would struggle to find traction to get going again. Occasional patches of ice were an added complication. I managed to reach the halfway (60% ?) mark where there is the small lake and the Maggi point, but didn’t proceed further on the even steeper and narrower last section.

Small short geared petrols like Alto and Ignis as well as diesel cars with light turbo like Trax etc will always have an inherent advantage over cars like Compass whose power delivery is very peaky in comparison and gearing is way taller. Again, EV with max torque instantly and at all times is the best solution.

[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.

Why do it? Sometimes you have very fragile cargo that can react to bumps with violence, may as well let the Jeep take it than the back of my head.

[purohitanuj]

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.

Why do it? Sometimes you have very fragile cargo that can react to bumps with violence, may as well let the Jeep take it than the back of my head.

The stock tyres have no relation here.

Infact, all part time 4WD specifically warns user not to drive on 4WD mode on high friction surfaces.

When you say you have driven, I am assuming it's on a straight road ( or many points turns). Any 4WD driven in 4L with full steering turned on paved roads will cause extreme stress on diffs / axles / Transmission. The weakest point will fail sooner or later in this case.

I do get the point that while climbing, the front tyres may lift (due to load transfer on rear axle) a bit and allow slight slippage; but I am not willing to bet on that when there is a work around available. Even in that case, one has to do multi point turns which might not be feasible option at times.

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

[svsantosh]

Originally Posted by purohitanuj

My post has nothing to do with torque steer.
Consider what happens in RWD at all times? 100% torque to rear wheels. Hence, I would request you to please elaborate your question.

Is the primary reason of this mod to eliminate the transfer case driving the front axles? Because the car tends to go straight when all 4 wheels are in 4L?