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ETC vs Double ARB lockers


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Hi Again!

I have a question that has been in my mind for a while now and I am interested in the opinion of people in Britain since I imagine there are already quite a few Defenders with ETC travelling around your country, not many down here yet.

My question is as follows:

Given two exactly identical Defenders (90 or 110, whatever) what´s going to be more capable off-road:

a) the Defender with ETC (original LR, installed from factory)

OR

B) the defender with ARB lockers in the front and rear diffs

If you have an answer please explain WHY?

I personally have 2 ARB's installed in my Defender 110 Td5 (now with a Brazilian 2.8 HS International engine) and it is awsome off road but since I do not undertstand exactly how the ETC works I cannot understand (or fight back!!!) when some people tell me that an ETC equiped Defender is even better than one with double ARB lockers.

What advantages and disadvantages would both sistems have?

Thanks for your help!!!!!

Cheers,

Santiago

Argentina

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Hi Gus,

Let me see if I understand:

ETC plus double ARB is the best option, OK, got it, not one or the other but actually both, makes sense.

I actually hadn't thought about it.

Now, going back to my original question:

Are you saying that based on the experience with your own vehicle if you have to choose between ETC and ARB, you say ARB is better? (I did not understand). If so, can you explain why?

And by the way, why does a double ARB make an ETC equipped Defender a better vehicle, isn't ETC supposed to take care of everything regarding traction control? Or put the other way round why does ETC on a double ARB equipped Defender make it a better vehicle? Shouldn't a double ARB equipped Defender have the ultimate traction available?

Cheers!

Thanks

Santiago

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Not based on experience, but I think ETC is better.

When i.e. one of your rear wheels has lost traction it will keep spinning and also the other one will lose drive.

With a locker the other wheel will also keep spinning and may have some drive, but also the other wheel will keep spinning and may dig itself deeper in.

With ETC the wheel without traction will be braked, so that won't dig itself further in, and traction will go to the other wheel.

And not only on the axles, but also with the middle diff.

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Just some of my thoughts, it doesnt necessary answer the question though but hopefully food for thought.

it depends on whose driving and if they know how to and when to use ARBs compared to what to do to get the most from a TC equipped vehicle.

ARBs will give all 4 wheels turning at the same speed

TC on a defender works across each axle NOT between all 4 wheels so it will get you two wheels on each axle turning the same speed but not necessarily all 4 wheels turning the same speed. (LR2, RRV and T5 platforms are across all 4 wheels)

With either system if all 4 wheels have lost traction it doesnt make any odds anyway!

TC is a reactive system, ARBs should be used as a preventative measure.

TC is kinder to the drivetrain of a vehicle

i did post up a bit about how TC works a while ago but cant now find it but in short:

Using the ABS it monitors the speed of the wheels and compares them across the axles. When one wheel starts to loose traction (ie go faster) it applies the brakes to that one wheel, this slows the spinning wheel and also turns it from the path of least resistance to the the path of greatest resistance when compared to the other wheel on the same axle. The power then takes the 'new' least path of resistance option and goes to the other slower/stationary wheel that has traction.

All of this uses power from the engine (lost in heat etc through braking) so you need to accelerate to over come this power loss. By accelerating you would also spin the lost traction wheel quicker which means the TC will brake it quicker and harder therefore transferring the power to the other wheel quicker. Its a reactive system as you need to spin a wheel first.

A locking diff as the name applies just split the power 50:50 straight to either wheel, but you would engage it prior to the obstacle and use it as a preventative measure.

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A few weeks back I was invited down to a LR Driving Experience Centre for a half-day on/off-road with their 57-reg Defender 110 XS.

I specifically asked my host, the Manager of that Centre, whether ARBs were now any additional advantage as the vehicle had ETC. His opinion was No. I presume all the DE Centres have to use standard-fit Defenders, and they'd reckon they have good examples of all/most tricky conditions. They're also doing courses at various levels all day long and I'd guess they could be considered pretty expert.

He demonstrated with one front wheel on a pair of heavy duty rollers, with ETC on and off (he had a trick/undocumented way of turning it off - some ECU sequence I presume) and with the centre diff locked and unlocked.

I'm no expert in any way in this area. You would think that ARBs may help just a bit extra in some form of extreme situation, but as the ETC logic would not be aware of their presence, you might easily bring on a conflict that actually degrades the overall ability to remove oneself from some muddy hole?

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You would think that ARBs may help just a bit extra in some form of extreme situation, but as the ETC logic would not be aware of their presence, you might easily bring on a conflict that actually degrades the overall ability to remove oneself from some muddy hole?

If an axle is locked both wheels have to turn at the same speed therefore TC wont do anything, so there wouldnt be a conflict.

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It has long been a bone of contention with me calling a Land Rover "4 wheel drive" since becoming stuck on my own front lawn on a slight incline in my brand new Land Rover with 1 wheel spinning!. It took me a while to understand how the drive actually worked and I then wrote to Land Rover. I received a curt reply saying take some off road driving lessons and fit more appropriate tyres, vehicles are used all around the world and no one else has complained!

A couple of years later Land Rover introduced the centre diff lock. This created a vehicle with a 2 wheel drive capability. What is important in my opinion is how many wheels are driving when really needed, not when driving along on dry tarmac. I am unsure whether ETC has been available on the Defender as an option previously but now it is. This creates a vehicle capable of putting the drive where it is required. Must be a major step forward and surely only a matter of time as with the centre diff lock until it is fitted as standard. So Land Rover have obviously had a change of heart with regards to their reply to me of 25 years ago!

I do have an elementary understanding of the issues but am unable to comment regarding whether ARB or ETC is best. They both seem to achieve what I expected the vehicles to do 25 years ago.

Although in my opinion a Land Rover has not being made complete/capable of achieving its full potential without ARB or ETC it is surprising how few are fitted with ETC. If you look on the dealers used Land Rover site you will note about 250 Defenders for sale but only 1 has ETC.

The issue for me is really being able to obtain a reasonable insurance quote. If I advise my new vehicle has been fitted with a Land Rover optional extra the insurers will not give it a second glance but if I say the vehicle has been modified with the addition of ARB lockers many insurers will not be interested and others will require an extra £200.

MINESAPINT

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I received a curt reply saying take some off road driving lessons and fit more appropriate tyres, vehicles are used all around the world and no one else has complained!

Seems reasonable :ph34r: it's in the manual for most vehicles I believe :unsure:

ETC is very, very good for most things especially when matched with some decent tyres. We've had P38's, Disco3's and a new Range Rover turn up to club days on road tyres and they will go an incredibly long way, often they will get further than a normal Defender on aggressive mud tyres.

Lockers are, however, always going to be the ultimate way to deliver 4WD. You can't really get a more definite method of transmitting power to the ground than locking all four wheels together.

LR (and other manufacturers) often shy away from fitting true ARB-style lockers that are manually engaged as it requires extra hardware, strengthened components especially in the front axle, and if the driver is an idiot (and a lot are) they will leave them engaged at the wrong time and blow parts of the drivetrain up, leading to warranty claims and disgruntled customers who can't understand why their 4x4 isn't "really" 4WD.

The latest RR/RRS and Disco 3 at the top end have lockers but they are automatically engaged by the Terrain Response computer to avoid driver cock-ups.

One thing lockers can't do that the ETC/ABS/HDC system can is control your speed downhill and keep you on a straight path. Strictly speaking HDC is a different use of the ETC system, but then the ETC system is mostly just a new program for the ABS computer anyway. HDC uses the brakes to keep your speed very low down hill without losing control and I would say it gives a safer and more controlled descent than engine braking alone, even with lockers in.

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There are many instances off road where being able to generate wheel-spin is desirable, just as there are instances where having ABS is VERY undesirable. As with all electronic aids to driving they will help most of the people most of the time, but taken to the extreme the choice of manual control over everything is definately preferable.

Have you seen those Icelandic boys driving over the surface of the water without sinking.... now try that with ETC :lol: :lol: :lol:

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He demonstrated with one front wheel on a pair of heavy duty rollers, with ETC on and off (he had a trick/undocumented way of turning it off - some ECU sequence I presume) and with the centre diff locked and unlocked.

Isn't a trick... or anything that special:

Traction Control can be disabled by operating the brake pedal ten times within ten seconds, when the ignition is turned on.

Traction Control will be re-activated when the ignition is turned off then on again.

Ian

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The biggest problem with ETC is that it relies on wheelspin before it will start operating. In some off road conditions (like here) once the wheels start spinning on a hill climb etc you are finished.

It is better than not having ETC but a Defender with just the centre difflock will outperform a Discovery with ETC on all four wheels never mind if you fitted the Defender with axle lockers as well.

There is also the issue of the "three bongs" being "a bit of a problem" on ETC equipped vehicles. The system in my Discovery works fine most of the time but tends to panic and then shut down when things get out of hand. Not a lot of use really.

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Steve, you beat me to it (as usual). Basically the ETC does not go along with "Tread Lightly" at all as it requires lots of wheel spin to work. AND it only works if the ABS works, which can be not very often. And if the ETC doesn't work you are back to one-wheel drive, which won't get you far in a few places I go to. So unless you want to come back on a flatbed truck, either fit one or two diff lockers or stay in the shopping malls.

ps we did have a Disco trucked in on a TATA the other day and all had a good laugh.

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It is better than not having ETC but a Defender with just the centre difflock will outperform a Discovery with ETC on all four wheels never mind if you fitted the Defender with axle lockers as well.

i think so.

You can stop ABS / TC with a switch connected to the abs fuse in the fuse box. The switch will break the power supply to the ABS ECU, and when you return the supply, the TC will run again, in real time and is not necessary stop the car.

Usually, I disconnect ABS when driving downhill with mud, ice, or snow, because the ABS is a bit stupid and a lot dangerous in these situations. But when we drive up, the TC is a very good aid, only if the trail don’t have one meter holes or one meter stones.

However, in extreme situations, the TC is like a rich uncle in Australia (I live in Spain), It’s useless

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In some situations my standard DII on at's performs better then my 110 300TDI on 255-85-16 MT's. We were on a very slippery muddy field with a lot of land rovers lately, almost everyone got stuck, all defenders with big MT's. I expected that I would get the most stuck of everyone as one of the only disco's and without mud tyres, but the Disco kept on driving. Ofcourse my TC light was on constantly, but I was one of the very few who got out without help.

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It is better than not having ETC but a Defender with just the centre difflock will outperform a Discovery with ETC on all four wheels never mind if you fitted the Defender with axle lockers as well.

D2 or D3?

in my experience a shop std D3s will out perform a std and midly upgraded Defender off road hands down (regardless of whether the Def has TC or not). A D2 however would be lagging behind a Def in my opinion.

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Thanks for all the great data and opinions, I am learning a lot.

It seems like there is a big difference between the electronuc traction control of a Discovery 3 and the ETC of previous Discos and Defenders (optional).

If I did not get it wrong Discovery 3's have electronic traction control but also include (standard, from factory) electronically controlled diff lockers. Then, the interesting (and more or less fair) comparison to do would be: a Defender (or older Discovery) with double ARB against a Disco 3 (with lockers included anyways).

Am I correct?

Any guesses on what should peform better?

Anybody knows if the optional ETC system available for the 2008 Defender (Puma engine equipped) also includes electronically controlled lockers? In other words is it exactly the same traction controll system that comes on Discovery 3's? If this is not the case I suspect that a 2008 Defender equipped with double ARB's and no ETC should outperform (in heavy off road situations) a 2008 Defender with ETC and no lockers. Anybody agrees?

Finally, from previous comments it sounds like a double ARB and ETC equipped Defender wouldn't make it more capable off road than if it only had 2 ARB's and no ETC. The only benefit would be having the option to choose between ETC or ARB use, but this would not necessarily imply having more off road capabilities. Am I correct??? :huh:

Cheers

Santiago

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i think so.

You can stop ABS / TC with a switch connected to the abs fuse in the fuse box. The switch will break the power supply to the ABS ECU, and when you return the supply, the TC will run again, in real time and is not necessary stop the car.

Usually, I disconnect ABS when driving downhill with mud, ice, or snow, because the ABS is a bit stupid and a lot dangerous in these situations. But when we drive up, the TC is a very good aid, only if the trail don’t have one meter holes or one meter stones.

However, in extreme situations, the TC is like a rich uncle in Australia (I live in Spain), It’s useless

Gus,

Do you recon that with 2 ARB's your Defender is capable of very difficult climbs that it cannot achieve with only ETC connected? What model is your Defender?

Thanks

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latest Defender has ETC/ABS no electronic axle diff locks are available.

Diff locks will be better over ETC.

One of the downsides to diff locks is as James said, the driver remembering to put them in. Another is the lack of steering when the diff lockers are in. Lastly, diff locks can cause more drivetrain breakages compared to an open diff using ETC. For example if a wheel meets an immovable object, like a tree root, on a diff locked axle - it's still getting drive so something has got to give.

As has been said ETC can be easily caught out, such as crossing a deep ditch, where you can't generate enough slip to start ETC. In other sitautions like going up a steep slippery incline where there are no ruts TC will slide the vehicle from side to side, not so good when there are trees around.

A good mix is to have a rear locker with ETC. Then you get some traction to front wheels but you can still steer.

Cheers

Steve

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On the puma I've noticed the ETC comes on earlier than the Td5.

Trialling in 1st low with the engine on tickover it will still stop a wheel spinning if it starts to slip or loses contact with the ground. So the new system seems to need hardly any spin before it kicks in to keep you going.

So where as the Td5 needed a bit of throttle the puma will climb things on tickover with the ETC working away, and from my experience so far it is very effective at very low speeds over very rough ground.

ARBs are better if you know when to use them, but no point in both as with the diffs locked the drivetrain can't let one wheel turn faster than the others anyway, so you'll never have the ETC working.

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situation where twin difflocks will outperform ETC climbing sand dunes reason the last thing you want is any wheel spin, especially with MT tyres

I have twin maxidrives with correspondings axle shafts and cv . never broken anything. The other advantage is V8 lots of torque at low engine revs without having to wait for turbo to spin up.

The only downside is with twin difflocks in effectively no steering so its get the line right before starting climb. JMHO based on experience :D:blush:

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D2 or D3?

in my experience a shop std D3s will out perform a std and midly upgraded Defender off road hands down (regardless of whether the Def has TC or not). A D2 however would be lagging behind a Def in my opinion.

I was referring to a D2 in this particular case but as I said it depends on the conditions and yes it is doubtless true that in "some" conditions a D3 with its sophisticated traction control system will outperform a Defender's relatively archaic one.

However the only way I can see to get 3 tons of D3 through a swamp is by fitting a skirt around the outside and turning it into a hovercraft as no amount of electronics helps if you can't get the doors open on either side :)

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