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Using the differential lock when climbing a high dune


Atif

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Is it useful to have a locked differential when climbing a high dune? This was mentioned by one Carnity member when driving his Patrol up on the second attempt when he was successful using a locked one.
Prado offers only a central diff lock so how much difference is it to the Pajero’s options?

As per my understanding in a locked differential the torque would wary so as to transfer to the tyre with the maximum grip i.e resistance thus it should be more effective.Am I correct?
However, I don’t know if locking it while side sloping would be detrimental.

 

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Central diff-lock (technically) will help in climbing tall dunes. Only in HLC (High-Locked) NOT in LO gear.

In reality the marginal (fractional) advantage might show or not depending on the same line you take with exact same speed in both attempts. Taking about faya attempts, here.

At times I do climb tiny bit higher with central diff-lock on and at times, I don't. Even when I do its by few meters only and not any substantial gain.

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To have a clear picture, open diffs means that each wheel has different power depending on how your vehicle requires it, so in the instance of going in a circle, the tires on the inner side will rotate fewer times than the tires on the outside of the circle. With open diffs the vehicle in case of stuck gives more power to a freely moving wheel and takes away power from the wheel which is stuck. When you apply the difflock the vehicle provides the exact same power to all the wheels irrespective of whether they are free or stuck. This helps us to create a little movement when stuck, which allows us to rock the car until we have enough momentum to come out of the stuck position. Try turning a circle with the difflock engaged, you will feel one side of the vehicle skip as all tires are rotating at the same speed.

I would personally not recommend to climb any dune with the difflocks on, on a straight up you may engage the diffloc as @Gaurav bhai put it in high gear and not low to get a little assistance, however if you are unable to make it to the top turning from the height with locked diffs can have a lot of load on the shaft of the vehicle. So stop and reverse back all the way. I would not at all recommend doing sideys with the difflocks on as some amount of steering is required to manage any sidey.

@Gaurav bhai's Pajero is special and has both rear and central difflock, it is from an era when Pajeros were ruling the Dakar and most of the technology made it to the top end models. The newer Pajero only 3.8 liter version comes with rear difflock only. Central difflock locks from the middle thus giving each tire the same amount of power. Pajero with the rear difflock means it only locks the rear wheels, which means the rear wheels power is equally distributed. However I would highly recommend using difflocks in case of stucks only and not while doing other maneuvers or climbs.

For climbs I would recommend you give yourself and your vehicle some time. We normally approach a big climb or play area after doing some desert driving, even if all the readings show normal there is some heat trapped somewhere which kind of eats into the power. While you are waiting for your turn open the bonnet of the car, switch off the engine for a while. Check your tire pressure, as after about 1 hour of drive you might have gone up 2 or 3 PSI on tire pressure. Adjust your tire pressure. Open and inspect your air filter and make sure it is clean, just gently tap against your tires to make sure any dust is off. Start your car and try to climb, it will give you much better result than just using the difflock for an easy climb. If I remember correctly @Atif bhai the last time we were at Faya you took it head on and succeeded, there is no comparison to making it to the top with just the steps as I have described rather than putting unnecessary toll on your car components. You cannot beat me at being a loser as I can never climb up Faya or Iftar Bowl straight up, that is why I choose to make myself some cheat routes.

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Good point clarified @Rahimdad

@Atif You shouldn't use rear diff lock for any climbing or driving.

However you can safely use center diff lock for climbing or even on normal desert driving where you constantly need to negotiate hard with cross tracks, steep sudden climbs etc. for better grip and stability.

With central diff lock ON engine power is getting equally split in front and rear by 50:50 without locking any wheels, so you can also safely turn freely while central diff lock is engaged.

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54 minutes ago, Gaurav said:

Central diff-lock (technically) will help in climbing tall dunes. Only in HLC (High-Locked) NOT in LO gear.

In reality the marginal (fractional) advantage might show or not depending on the same line you take with exact same speed in both attempts. Taking about faya attempts, here.

At times I do climb tiny bit higher with central diff-lock on and at times, I don't. Even when I do its by few meters only and not any substantial gain.

Both @Gaurav Bhai and @Rahimdad Bhai have good advice and if at all I try using diff-lock for climbing a high dune it would be on a second attempt and only if going up straight. I also feel it might not give too much of an advantage. 

So best is to keep the diff lock usage mostly when getting stuck.

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2 minutes ago, Atif said:

Both @Gaurav Bhai and @Rahimdad Bhai have good advice and if at all I try using diff-lock for climbing a high dune it would be on a second attempt and only if going up straight. I also feel it might not give too much of an advantage. 

So best is to keep the diff lock usage mostly when getting stuck.

Central diff-lock you can use it any time and take turns too (not only on straight incline) as its locking the central drive shaft for equal front and rear power split without locking any wheels.

But don't use rear diff-lock for normal driving.

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Just now, Gaurav said:

Central diff-lock you can use it any time and take turns too (not only on straight incline) as its locking the central drive shaft for equal front and rear power split without locking any wheels.

But don't use rear diff-lock for normal driving.

10 minutes ago, Gaurav said:

Good point clarified @Rahimdad

@Atif You shouldn't use rear diff lock for any climbing or driving.

However you can safely use center diff lock for climbing or even on normal desert driving where you constantly need to negotiate hard with cross tracks, steep sudden climbs etc. for better grip and stability.

With central diff lock ON engine power is getting equally split in front and rear by 50:50 without locking any wheels, so you can also safely turn freely while central diff lock is engaged.

The Prado has a central diff lock only. I am not sure if the torque is split 50:50 as I overheard someone say it isn't but as I said I would mostly use it either in a completely stuck or as you indicated "negotiate hard with cross tracks" . 

However, if the central diff doesn't lock any wheels i.e. if front set is completely in air would the torque be available for the rear set? I am finding it hard to imagine the working of the central diff lock so need to see it in practical use sometime. I do grasp the point about rear diff lock or front diff lock though.

 

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Every car manufacture do and try different power splits like 60:40, 66:34, 70:30 based on the engineering for power and fuel efficiency.

As many use 4x4 for mountains and trailer load etc.

Whenever you engage central diff-lock in all vehicles (to best of my knowledge) it create a 50:50 split, increasing the chances of countering slippage (loose track) or struggling in sudden steep hill climb without enough momentum.

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@Gaurav bhai and @Rahimdad bhai  

in case of no diff lock ( my X is lacking it ) what is the alternative ? in other words is there a way or trick that may simulate the diff lock ? .. off course we are talking here about the stuck situation ( except central crest stuck ) 

Edited by Mohamed Seidam
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