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Diff locks (operation)

[ Adam ]

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255/85

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Did they have the electronic traction aids turned off? Electronic stability control should work in 4hi, right?

ESC has various modes on the Grenadier (going from memory)...

In normal driving with the CDL unlocked you get standard ESC "ON".

If you engage "Offroad Mode", "Wading Mode", or press the "ESC OFF" button you get "ESC Offroad Mode" and reduced ESC functioning.

If you lock the center differential I think you get "ESC Offroad Mode". If you then press the "ESC OFF" button you turn the ESC off completely.

If you engage "Low Range" then ESC is turned completely off. ESC is not available with the front or rear cross-axle locks engaged.

I may have some of this wrong or have over simplified. Ineos released a video explaning things in their Getting to Know videos with the youngish rep demonstrating. I seem to remember seeing the videos on the Abenteuer4X4 web site among other places.
 

255/85

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I understand the concept. What I don't understand is how a full-time 4x4 can be stopped dead in its tracks with one tire on a roller.

Correction: What I don't understand is how a full-time 4x4 can be stopped dead in it's tracks with one driven tire on a roller.

This is no different than any of the other old school 4x4s you've mentioned above. Your passive front wheels on your 40 or your CJ in 2Hi were liabilities from the get go.

f1: front left tire with no traction
Grenadier is stuck
Jeep Wrangler drives away in rear wheel drive

2: front right tire with no traction
Grenadier is stuck
Jeep Wrangler drives away in rear wheel drive

Correction: The Jeep Wrangler drives forward the length of it's wheelbase (like six feet) and is then stuck too.

3: rear left tire with no traction
Grenadier is stuck
Jeep Wrangler is stuck

4: rear right tire with no traction
Grenadier is stuck
Jeep Wrangler is stuck.

In HI/Unlocked Grenadier's traction control should kick in which was unavailable in the old days. Were they in Low Range in the video which might have shut off the ESC?

I am really surprised by the poor performance of the Grenadier on a single roller - with the center diff open. Of course, Audi Quattro is a road-biased all-wheel drive system, designed for different use than the Gren or any other off-road 4x4. But if one was to compare apples to oranges, the Audi can drive away with three tires on rollers (i.e. only one wheel getting power).

So what's my point? Its not to bash on the Gren - so no need for anyone to feel defensive. On the contrary, full-time 4-wheel drive was one of the features of the Gren that - in my mind - put it above part-time 4x4s like the Wrangler. But the demonstration in this video suggests to me that - when driving on roads that alternate between "decent traction" and "poor traction" (common in the winter around here) - one will need to lock the center differential in the same way that one shifts into 4-wheel drive in a Wrangler, Tacoma, or any other part-time 4-wheel drive. To me, that is both surprising and disappointing. It had been my assumption that the Grenadier's "full-time four wheel drive" system was going to be better than this test makes it seem, and that it would be a significant step up from a part-time four wheel drive vehicle that needs to be shifted in and out of 4-wheel drive on wintry roads.

Yes, the only real solution is shifting to 4Hi or locking the center differential. But barring that, when experiencing mild traction loss at speed and there's some momentum to the vehicle, a traditional rear drive vehicle will fishtail a bit more than an all wheel drive model. Very modest differences to be sure and more of a British vs. American mindset really.
 

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@255/85 said "Correction: What I don't understand is how a full-time 4x4 can be stopped dead in it's tracks with one driven tire on a roller."

Totally agree.
 
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@255/85 said "Correction: What I don't understand is how a full-time 4x4 can be stopped dead in it's tracks with one driven tire on a roller."

Totally agree.
Well, to be accurate, it is redundant to say "driven" when you have already said that you are talking about a "full-time 4x4", but who's counting :)
 

Xrford

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I would like to summarize why full time 4x4 is better than 2wd using an example. I am using made up numbers here so do not get hung up on the actual numbers I use here, and my example assumes no electronic traction control intervention. Also since I have never seen a roller sled occur naturally out in the wild, my scenario is assuming there is more than zero traction (ie ice with snow or dirt on top, loose gravel etc).

Assuming the full time 4x4 (centre diff unlocked) rolls up on this snow covered ice obstacle with one wheel on the obstacle, if this obstacle offers up 100nm of traction/torque , and assuming the required torque that is needed to move the vehicle forward is 400nm then the full time 4x4 will move forward because each of the other 3 wheels will also be able to apply a 100nm of torque. However the part time 4x4 in 2wd will only be able to apply 200nm of torque (with one of its rear wheels on the obstacle) as it can only apply the 100nm to the other rear wheel and will be stuck. The real world rarely has zero traction, so although these roller scenarios are advantages for demonstration purposes they should not be used to generalize how a vehicle will behave in most real world scenarios. In the large majority of real world scenarios full time 4x4 is superior when there is low traction, all other things being equal.
 
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AnD3rew

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Open differentials (without traction control) send power to the axle (or drive shaft) with the least amount of grip or resistance. Whether that be three open differentials (like the Grenadier or Defender) or a 2wd Jeep with only the rear differential powered. Only by locking ANY differential (front, center or rear) do you split the delivery of the power across the differential. By locking the center differential you split torque 50/50 between the front and rear, and by locking the rear you will split torque between the rear left and right. The same applies for the front.

This is why, based purely on mechanical, open differentials the Grenadier was immobilized by lifting a single wheel.

The Grenadier does employ "brake traction control" or ETC, as illustrated in this video:
View: https://youtu.be/lLFzv7FJy3g?si=oDZ94pqqzP1PudvU&t=332


My assumption is that in the previously referenced video, they have turned ETC off (if this is possible) for purposes of illustration. Brake traction control, coupled with a locked or unlocked center differential can be quite capable. - as illustrated here:
View: https://youtu.be/LUdQ4WgRbgE?si=T9sxYdoBiFYn82q-&t=60


Regarding "all-wheel drive", it really depends on what system you are using. Modern "all-wheel drive" systems simulate locking differentials by monitoring the wheel speed sensors and applying the brakes and/or by using limited slip and or electronic locking differentials in the front, center and rear.
I agree, the traction control must have either been off or faulty. You can see in the Robert Pepper video that while it is a little slow, the traction control does work.
 

AnD3rew

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Do we have an answer why front and rear diff locks only work in low? Can someone please explain me the logic behind it? I am sure Ineos has a very good reason but I don't get it.
I think it is an idiot/carelessness protection system to reduce the risk of you operating on road at speed. However I would prefer they didn’t do that, as I have already experienced a reason why its potentially a problem. I was deep into a pretty knarly track that I had up to that point traversed in high range, I then came across a section of washout and steep bank and decided I wanted low range. Went to shift and it entirely failed to engage. (Centre diff was locked and was possible to shift. ) that was unfortunate but then I thought I woul just lock the diffs instead to get me through, but of course you can’t. Fortunately for me, the truck is so capable it handled it all in high range with only centre diff locked. (I had winch as backup option) but you can see how that just removes another option if you have a failure, arguably unnecessarily. I had to have transfer case replaced in the end. I wonder if it is possible to identify where the switch/sensor is that tells the car that it is in low lange and allows the diffs to lock and add an override switch?
 
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Do we have an answer why front and rear diff locks only work in low? Can someone please explain me the logic behind it? I am sure Ineos has a very good reason but I don't get it.
To protect people from themselves and having accidents at high speed. With the front diff lock engaged there is next to no steering.
 
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It would be interesting to know if Ineos considered a Torsen center diff with mechanical lock during the Grenadiers development. This addition may of prevented the one wheel drive scenario with the center diff lock disengaged.
 

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@255/85 said "Correction: What I don't understand is how a full-time 4x4 can be stopped dead in it's tracks with one driven tire on a roller."

Totally agree.
See Post #82...the English translation: explains it precisely

In summary: in the absence of an "intervention" such as traction control or for example a Torsen LSD on the centre diff, it wouldn't matter how many diffs or "driven" wheels you had: even a 6 or 8 wheel drive with multiple diffs: if all diffs are fully "open"/ unlocked and only one of the multiple wheels was on a roller /on ice/ in the air/ etc the vehicle would 'fail to proceed' because the applied power takes the path of least resistance and is therefore directed to the wheel with the least resistance. ....
 

PBD

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Has anyone had a problem with loss of power whilst their front and rear diff locks engaged? Mine kept dropping down to tick-over whilst in the mud and nearly left me in the SH1T!
Along with the sever problems when disconnecting the diff locks, now decided they are unusable till fixed.
Also twice had the break peddle to the metal with no breaks! Both times in off road mode?
Mine is a very early version CN 697, do the latest versions coming off the assembly line still suffer from all the multiple problems?
 

rovie

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Has anyone had a problem with loss of power whilst their front and rear diff locks engaged? Mine kept dropping down to tick-over whilst in the mud and nearly left me in the SH1T!
Along with the sever problems when disconnecting the diff locks, now decided they are unusable till fixed.
Also twice had the break peddle to the metal with no breaks! Both times in off road mode?
Mine is a very early version CN 697, do the latest versions coming off the assembly line still suffer from all the multiple problems?
Hi @PBD my vehicle is comparable to yours in terms of assembly time. Both could see themselves on the assembly line. 😉I have driven with the differential locks switched on several times now and have not noticed any loss of performance. I am not familiar with the problem with the brake pedal. You should definitely have this checked.
 

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It would be interesting to know if Ineos considered a Torsen center diff with mechanical lock during the Grenadiers development. This addition may of prevented the one wheel drive scenario with the center diff lock disengaged.
Only if you have a 100 % locking torsen diff lock. The ones locking up to 75 % that I know will need TC for help as well if one wheel is spinning free.
 

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And as an answer to the original question „why an open 4 wheel drive is that bad when one wheel is in the air?“
It is better than anything else all the way towards this point. If your Grenadier stops with one wheel spinning any two wheel driven vehicles with similar technical specifications (weight, length, wheel size, power,…) will probably be far away in your back.
So from my understanding all time 4 wheel drive is a huge enhancement for driving security on every surface that is not dry tarmac.
 

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Just a thought - how would other all-wheel/permanent 4wd perform in the same roller tests.

Audi Quatro? Subaru? Do these even count?

What about JLR products like the Range Rover?
 
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Just a thought - how would other all-wheel/permanent 4wd perform in the same roller tests.

Audi Quatro? Subaru? Do these even count?

What about JLR products like the Range Rover?
The Audi All Road was able to move off when any two wheels were on rollers without any changes to driving settings. When three wheels were put on rollers, the Audi was able to move off the rollers after the driver engaged "off-road mode" (or whatever Audi calls it). In my mind, such an input from the driver is equivalent to a Grenadier driver locking the center diff. The video is below.

I have owned two Audis (2008 RS4 and 2012 S4), and for on-road driving in snow and ice, they were both far superior to any 4x4 I have owned (a few Jeeps, a 1975 Landcruiser, a 5.9 Cummins, and multiple Toyota pickups and 4-Runners) - as long as the snow isn't too deep (very little ground clearance).

EDIT: I found three Subaru slip tests from TFL (2018, 2021, 2023 - all below). I watched the oldest one - probably back when it came out - but I haven't watched the more recent ones.

What I wanted to find was a slip test for the Landcruiser 200, as this is a more relevant comparison to the Grenadier. Be cool to compare the "street modes" in each (i.e. "full-time 4-wheel drive" with the center diff open). Couldn't find it after a short search, and don't have time for a longer look.

All the best!

View: https://www.youtube.com/watch?v=eETlcqgtM4Q

View: https://www.youtube.com/watch?v=AdMEJI_4Whg

View: https://www.youtube.com/watch?v=WPBnhfh9HoM

View: https://www.youtube.com/watch?v=edVyk7TF7ro
 
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Just a thought - how would other all-wheel/permanent 4wd perform in the same roller tests.

Audi Quatro? Subaru? Do these even count?

What about JLR products like the Range Rover?
Ive enjoyed owning/driving a few of the above. My wifes outback wilderness has been very impressive out hunting this year (we had already sold my old TD5 defender and LR3) up loose grades as step as 21 degrees in the mountains in BC. Havent had it on rollers or a skating rink, but a few of those old skidder roads felt like driving on ball bearings. only once, on the 21 degree slope, did i need to turn on the 'offroad mode' of the traction control. This vehicle has blow away previous generations of forester and outback we had owned. The shape of the vehicles nose is a far greater limitation than its traction control or power, but has nothing to do with your question. The clearance is a limitation to get the vehicle into a real life situation with a wheel in the air (no resistance) so its not really a fair comparison.
The LR3 had mind bogglingly good traction control for such a brick of a vehicle, and had only gotten stuck in situations where all 4 would spin (briefly) to no avail, or the truck lacked power push through something. In the latter the vehicle may have done fine with a greater dose of inertia, but throwing the vehicle at things is not my driving style. I never experienced a wheel up that failed to be arrested by the traction control, or three wheels on the ground that couldnt move me forward.
My TD5 was old school and never failed me in low with CDL, though it certainly would spin a wheel.
 

ADVAW8S

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There is a subset people in USA that bought the Grenadier without the lockers. Their argument, which makes total sense, they never got caught in situation that they need them. Many of vehicles they reference had really good TC. It will be interesting to get their feedback as they get in woods with theirs.
 
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I am wondering if I will miss the Detroit TrueTrac in the rear differential of my Rebel. It is a gear driven (TorSen) limited slip (not the standard clutch style) which never lets me get stuck and is "automatic" when there is a difference in the torque driving one rear wheel from another. It is seamless and requires no driver button pushing. I wonder could such a TorSen differential be installed in the rear of the Grenadier so there is an option other than "fully locked or fully open"? I think the military HUMVEES used these differentials front and rear.
 
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