[Kosfactor]

All good points , but given the context of this thread - If the fellow who dropped off OP's Jimny realised his mistake and returned the lever to original position before handing over the keys - this thread would not have happened

OP would have never known about this mistake either, So gentlemen, I am not condoning violence against 4WD vehicles but such things do happen and yes for the sake of clarity - Please do not engage 4H on tarmac.

[arjithin]

Originally Posted by Vikram Arya

Well, you seem to have missed an important data point.

Mitsubishi's Super Select II system comes with a Centre Differential which stays open in the "4H" mode and is locked in the "4HLc" or the "4LLc" mode and that's why in the screenshot that you have enclosed it advises you to use those modes only in "Deep Snow, Muddy, Sandy, Rocky" surfaces. The open centre differential in the 4H mode will prevent any transmission binding from happening while diving on a paved surface in the "4H" mode.

Jimny as has been mentioned by several contributors here does not have a center differential and therefore the two scenarios are as different as chalk and cheese.

I'm disappointed by comments by some contributors almost saying that it's okay to drive in 4H on a paved surface in a vehicle that does not have a centre differential.

Massive thanks to Eric, Dhanush & Dr. Tejas to set the record straight.

I completely understand and agree with you. My post was about a generic statement in this thread that no part time 4WD can be driven on a hard surface in 4H mode. Jimny's case is different, but it cant be generalised.

I trust the engineers who design the system than few incidents of 'nothing happened'. Hence what is mentioned in the user manual carries more weight than few anecdotal evidence. I have seen a LC79 series driven in 4H on bitumin for 80km before realising the mistake and that car is still running fine after 90,000 km. That 80km was a motorway with minor curves but cant expect that to be the case for a winding hilly road.

Engineers have limitations on dummy proofing as well.

[Tejas@perioimpl]

Originally Posted by arjithin

Mitsubishi Pajero/Triton/Pajero Sport etc can be considered part time 4WD right? If yes the Mitsubishi super select II system allows 4H on tarmac upto 100kmph.

Lol. People got the point. We are talking about current breed of cars which have 2H, 4H and 4L. The ones with centre diffs have 2H, 4H, 4HL, N and 4LL where the 4H = 4HL

If you want to argue for arguments sake then I'm not getting into a further discussion with you

Originally Posted by purohitanuj

Drive your Jimny on 4WD mode only on surfaces that allow your tyres to skid easily. If the friction between your tyres and the surfaces is strong, don’t drive on 4WD because while turning, you are putting a lot of tension in the mechanism (that translates into a braking effect), which may damage your differential.

Exactly. I don't understand why people are arguing over a clear black and white statement.

Originally Posted by Kosfactor

Well, what if your friend borrows your Jimny, drives it on tarmac for 100 kms on 4H?!

What if he drives off a cliff? Don't argue just for the sake of it.

Originally Posted by Kosfactor

Now you see, such things happen more often than you think. Therefore, as long as your tires are stock and the vehicle is not overloaded, chances are nothing will happen.

It has happened to atleast two of our vehicles and they are doing alright, so OEMs have certainly taken such mistakes into account.

You are a Dbhpian. The statements you make get taken more seriously by uneducated readers. Tomorrow if people survive a horrible car crash without wearing seat belts, would you say, it's ok to drive without belts? NO.

With a badge, comes responsibility. I urge you to put down the right thing because this forum discussion will stay here much after you and me and people will still be reading this.

Originally Posted by Sheel

If it's your SUV and you have to lend it and you have not explained the workings / functioning of your SUV, who is responsible?

Touche'

Originally Posted by arjithin

I completely understand and agree with you. My post was about a generic statement in this thread that no part time 4WD can be driven on a hard surface in 4H mode. Jimny's case is different, but it cant be generalised.

Flogging the dead horse!

EDIT: Jimny gives a nomenclature of L for 1st gear and confuses newbies to select 4L or L at times not knowing which is which! So don't harp on simple pedantics when the point was on target in the current discussion.

[arunpools]

Originally Posted by Tejas@perioimpl

What if he drives off a cliff? Don't argue just for the sake of it.

Some thoughts that popped into my mind after going through some of the posts in the thread are as follows.

What if there are reasons why people have even suggested you could drive for a few hundred kilometres on the tarmac in 4H without any problems? I’m not saying that this is even remotely correct but their reasoning is justifiable. I believe calling these comments merely based on personal experiences is improper without giving sufficient consideration.

To start with let me show what Mahindra has to say about driving with 4x4 engaged in Thar.



The statement points to its usefulness on ‘dry pavement’ as well. I mean, to me dry pavement would mean tarmac too. Mahindra does warn against using 4H on paved roads (or whatever they meant by that) but the statement in the manual that my car came with says the reason for not engaging 4H is difficulty in disengaging back to 2H! Meanwhile, they warn against using 4L on ‘paved roads and dry hard surfaces’ because this may lead to transmission damage. That said, at other places in the manual they do say why the car shouldn’t be driven 4H on tarmac. Wow! I tend to read the manuals. To me this is absurd.

Saying that 4x4 vehicles shall only be driven by experts and for others there are other less confusing options like AWD and the selling hundreds of thousands of cars with the technology with an owner’s manual that would confuse anybody is a recipe for disaster. Or is it? I reckon if that was the case I would have seen many Thars with busted drive lines in the service centres already. But I don’t. Or is it that Thar’s transfer case and other components are more robust and are capable of taking more beating? I saw a fellow on YouTube doing a fuel efficiency comparo between 2H and 4H on a highway! The car was in good shape during the video but I don’t know what happened after that.

Let me give another example from Toyota. Now this time it’s Tacoma with its part-time four-wheel drive. The manual clearly says not to drive on dry pavement. However, the manufacturer adds to the confusion by stating that the car shall be driven in 4H at least for 16 miles every month to keep the front drive train components lubricated. There are many Tacoma owners bragging about on international threads who have driven blissfully in ‘4H in a straight line’ on tarmac just to meet the requirement because they don’t do offroading every other day. But they forgot to read the next part in the manual where it is clearly written not to drive on the tarmac with 4H engaged.

My ‘22 Thar has Eaton-sourced mechanical Locking Differential (MLD) at the rear axle. Amusingly, the manual says nothing about it (my owner’s manual doesn’t have it but now it seems they have finally woken up an added a few sentences in the latest downloadable editions of the manual)! The MLD is a centrifugally actuated device that locks and unlocks automatically. So, if I were to skid one of my rear wheels while driving uphill in 2H the MLD can get actuated automatically. The thing is MLD once locked will remain locked until the forward speed increases without tyre slip beyond 25kmph at which point it automatically disengages. Also, locking unlocking of the MLD is not advertised in any manner to the driver. No tell tail lights, nothing and absolutely no manual control on what it does. But when it does get locked you may perceive its action via a sudden jolt from the rear axle and that’s all.

Now, what if I was driving up a steep incline on a muddy tarmac road and the MLD gets actuated and I need to take a tight turn as well? Anyone who knows how to properly operate a vehicle with MLD knows that these things can be forced to disengage when driven in the opposite direction of the movement that led to its locking. So, I have to drive in reverse. Or I have to steer to same side of the wheel that slipped (so that I can go back to the ditch?) What if the situation doesn’t allow? The speed difference between the two rear wheels when making a tight turn is much higher than the speed difference between the front and rear axles during the same manoeuvre. In other words, the torsional forces in the differential are going to be tremendous. I’m not suggesting the situation with locked rear wheels is the same as a locked transfer case. But as a mechanical engineer who has already spent a considerable part of my adult life working in mechanical engineering design and manufacturing, it is natural for me to assume that the lockup system in the Thars’s rear axle is designed to take care of those one-off situations. Especially when the manufacturer thinks it's ok not to even mention anything about the feature and its functions to tens of thousands of customers. I’m not here to convince anyone who thinks that it cannot be designed for it.

It should be pretty clear to the manufacturers that most of the owners with 4x4 vehicles (part-time type or any other type) don’t have a clear understanding of how their systems work.

Let me explain what I have learnt as far as my car's part-time system is concerned,

1. 4H shall only be used if the situation calls for its use.

2. A high coefficient of friction doesn’t necessarily mean a high traction surface per se. The difference between the friction coefficients on tarmac (0.7-1.0) and gravel surface (0.5 to 0.8) for normal tyres is hazy and not different enough and should not be used to decide whether to use 4H or not. What part-time four-wheel drive vehicles need is a ‘low traction’ surface not necessarily a surface that offers a ‘low friction coefficient’. If the surface is uneven to the extent that one of the wheels can break free now and then, the surface is good enough. This is what Mahindra was trying to convey in their manual by saying ‘dry pavement’.

3. Drive train windup is a torsional force buildup in the dive train. That’s it. A part-time drive train in 4H will have windup all the time and just having some windup won't wreck the system but its magnitude and the time for which the system is made to operate under high stress matters. Driving on high traction surfaces will lead to severe windup and can brick your transfer case.

4. Drive train wind-up will happen in both directions of the turn in 4H on high traction surfaces. If one starts to hear funny noises from the tyres or from under the body, they should not try to turn to the other side to relieve the built-up tension in the drive line. In either direction of the turn, the front wheels want to outrun the rear wheels. That is how the steering geometry is designed in any vehicle. In other words, if drive line tension has built up over some distance of using the vehicle in 4x4 trying to turn in any direction would aggravate the situation. So it’s better to stop immediately and try to select 2H. If the lever won’t budge, very carefully jack one of the wheels to relieve the built-up tension. This is only recommended if you are somebody who knows what you are doing. If there is considerable tension in the drive line, sudden release of that tension can be dangerous.

5. Going in reverse also may not relieve the built-up tension in the drive line. It may give some relief which may allow you to take the transfer case out of 4H but just reversing may not be enough if the built-up tension is too high.

6. The thing that kills the drive train is the progressive build-up of tension in the drive line which makes the components operate at excessing loads over long periods and not necessarily a suddenly applied load. Progressive tension built-up will happen while driving on the tarmac because all the wheels have very high traction the torsional forces built up in the drive train cannot be relieved via any of the wheels at any time.

7. Torsional forces would start to build up even because of variations in effective tyre diameters caused by inflation pressure differences as already pointed out by another BHPian.

8. Understeer is always associated with driving in 4x4 hence the vehicle will respond unpredictably without reference to the surface on which the vehicle is being driven. Reduced speed in 4H is always recommended.

Over the obvious rules of driving a vehicle in 4x4, the list enumerated above is what I know and have understood from all that I have read, heard, seen someone doing and experienced first-hand. But if 4x4 is that flimsy of a thing that needs to be baby-sited and for that reason only used by experts, I wonder why I have failed to read most of these out of an owner’s manual. Owner’s manuals are like DIY for dummies at best. How can manufacturers assume that such a technology that needs expertise for its proper use think that they can get away with such useless and confusing owner’s manuals? If the argument is that most people won't understand these technicalities even if it is written in the manuals in black and white and these vehicles are going be abused anyway, brings me to my point. The manufacturer should have designed for the expected abuse or at least for those one-off chances where the driver unknowingly broke the ‘not-on-tarmac’ commandments. Fool proofing these things is not beyond the realm of mechanical engineering.

The whole discussion started with the OP stating that he unknowingly drove his in 4H on the tarmac. Though he shouldn’t have, the question is now what?

1. Whether he should keep driving his machine with the constant fear that it may fail on him at any time?
2. Open his drive train and check for damage.
3. Plug into the OBD port to see if there are any error messages.
4. Send the oils from all the assemblies on the train for inspection.

None of these makes any sense to me. If it works as before he should be good to go. Nothing much can be done. For the sake of argument, do they even cover 4x4 drive train components under warranty? Unless you can prove its a manufacturing defect they would call all problems with 4x4 regular wear and tear.

As Kosfactor pointed out earlier if the car was indeed driven in 4H during the test drives that the service centers do and slotted back to 2H before delivery, this whole thread would have never happened. This sort of a thing is very much real and if the manufacturer cannot oversee this and hasn’t already designed to take care of these one-off situations then at least give sufficient animated indication in the form of warnings that flash on the MDI once it detects prolonged 4H use.

I had an issue with my Thar a while ago and there was this huge engine check warning that popped up on the MID with an audible warning. There was no way I would have not seen that. If driving on the tarmac in a 4x4 for a few kilometres would wreck a part-time drive train it helps to keep one reminded through the MID that he is driving in 4H via animated messages and not merely a small unassuming 4H lamp in the dial cluster. Experts may not need it and may even find these annoying but most of the others who have bought these cars do.

Again, out of fear of sending the wrong message, I’m again re-stating the obvious that 4H shall only be used on low traction surfaces and never on tarmac. Even if you are sure your car has a beefed up transfer case than your kin’s, if your abuse didn’t wreck yours until now, it surely will later.