Differnece between 4H and 4L in sand

RaZe
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HI,
I know that this topic have been talked lot of times, but cant find any in this forum...:slow:

Any how,
My doubt is , if i am starting to climb a dune, what is the difference if i am in 4H and if in 4L.

Usually 4H and 2nd/3rd gears are used in sand driving, where do we use 4L while driving in sand?

I am having a fortuner 4.0, in the manual its written that if 4L is engaged we should not go beyond 20Km/h
4L and 20 Km/h would it help me drive through a dune.......?

[video=youtube;CQSwe56ylxg][/video]

in the above video, at 0:35 (he person mentions that the vehicle is not in low range ...?

Why does it need to be in low range?
Desert Lizard
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RaZe.. the difference between 4H and 4L is basically the gear ratio selected. In both cases, all 4 wheels are engaged, but 4L uses a lowers gear in your transfer case and produces more torque.

For normal driving in the sand, 4H is enough, and you will learn with practice the right combination of your transmission position and speed to climb up a dune. 4L is reserved for really steep and high dunes and situations where the car is stuck or trying to pull someone from a stuck.

Shifting between 4H and 4L requires a complete stop, and although some car manufacturers state that you can switch between them at very low speeds, ie 2Km/h.. you might just as well stop completely, then shift to 4L then continue. This prevents any possible damage or accident.

As for the video, the car is stuck, and as I mentioned earlier, going to low gear is something we do when a car gets stuck. However, in this particular example the car speed was low to start with, so you can drive on 4L if your going that slow..

Hope this helps
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Green Giant
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Raze, although I am sure the vastly experienced Marshall's will answer you, my understanding is that 4L is primarily for use in rocky conditions, ascending/descending rough mountain tracks and wadis. From a practical perspective, I have used it a couple of times to 'crawl' out of a stuck situation in sand when normal self recovery doesn't work. For sand driving, it is generally the combination of correct tyre pressures, momentum and driver skills which keep you out of trouble! The Almost club will educate you more every time you do a trip!

see you in the sand.
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caprihorse
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Forget the video, it's just advertisement as the pulled car's tyre pressure is just high. Australians in Australia have no idea about deflation in sand driving.
But coming to your question 4L or 4H. In 99.9% you need only 4H, as climbing the dune is the matter of momentum, right speed at the right place. 4L is required only when car is in trouble, self recovery (not to burn clutch or to get more torque) or at pulling, to give additional support to pulling car. However at self-recovery, it has to be used very carefully, not to dig yourself with extensive torque much more in liquid s**t.
Some cars, equipped with diff-locks, can use diff-locks only with 4L, like FJ or Fortuner, which is mostly useful in a self recovery, where the car is positioned sideways vertically, where you can try to go down with the gravity. In flat area it won't help at all, you'll be just digging more into sand. This is always sign that the tyre pressure is too high. See the video again carefully.
RaZe
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caprihorse;29400 wrote:Forget the video, it's just advertisement as the pulled car's tyre pressure is just high. Australians in Australia have no idea about deflation in sand driving.
But coming to your question 4L or 4H. In 99.9% you need only 4H, as climbing the dune is the matter of momentum, right speed at the right place. 4L is required only when car is in trouble, self recovery (not to burn clutch or to get more torque) or at pulling, to give additional support to pulling car. However at self-recovery, it has to be used very carefully, not to dig yourself with extensive torque much more in liquid s**t.
Some cars, equipped with diff-locks, can use diff-locks only with 4L, like FJ or Fortuner, which is mostly useful in a self recovery, where the car is positioned sideways vertically, where you can try to go down with the gravity. In flat area it won't help at all, you'll be just digging more into sand. This is always sign that the tyre pressure is too high. See the video again carefully.
CHief,
You were right about the tyre pressure..
i should stop seeing such kind of videos and be practical to find out my self......

Its always good to know from the best.......:thumbsup:
Thanks chief.....
jehan
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And just a reminder Shifting to 4Low and out of 4Low requires the transmission to be neutral.
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caprihorse
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jehan;32095 wrote:And just a reminder Shifting to 4Low and out of 4Low requires the transmission to be neutral.
This is required for specific models, mostly equipped with automatic transmission.
All models equipped with manual transmission don't need to have main gear in neutral, just car needs to be stopped, not moving at all.
lizzy
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You should shift into low range in anticipation of difficult terrain ahead. Low range gives you more engine torque at lower speeds and thus allows you to travel slower and in more control, depending on the surface you're driving over.

20km/h seems excessively slow for the maximum speed in Low range. Most 4x4s should manage at least 40km/h in 5th gear without exceeding 2500 rpm. Specifically you should be in Low range and 1st or 2nd gear when descending long slip faces. This is allows engine braking for the descent, allowing better control and the ability to quickly correct a slide.

Also some cars need to be moving in order to switch between low and high, some need to be stationary.
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caprihorse
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In normal driving you should use only 4H, even if the area in front looks steep. With speed and momentum you can achieve better climbing and car control. With engaged 4L the car is slow and tends to dig more into the sand. 4L should be used only in stuck situation, if the terrain allows it. Sometimes, when you are sitting in a short ditch, with nose stucked into the sand wall and steep area behind you, even 4L will not help you.

At long descends (mostly in LIWA) SWB's are using 4L, but this is not necessary always. LWB's and standard length cars are safe with 4H. At any moment it is important to control car steering with throttle and turning softly front wheels against car's direction and reduce braking to the minimum. The sand friction is in many cases enough to slow down the car.

I never saw any 4x4 car, which can switch between 4H and 4L on the fly.
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