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- Labbix
- Member Since: 05 Mar 2018
- Location: Tanzania
- Posts: 955
Added value active rear diff lock
Hi All,
I know how traction control works and diff locks, but when I think a bit more I really start to wonder what the real added value is of the active rear diff lock if you already have a centre diff lock in combination with traction control, like the D5, and front locks are not provided from factory anyway.
The only thing I can come up with is a better control of momentum with the extra rear diff lock, as traction control only starts working if traction is lost (and therefor momentum most probably).
So traction control is a tool to ‘fix’ non traction and not at all prevention of non traction, while diff locks are in this regard more a preventive aid to maintain traction and momentum.
So in deep snow or on a very muddy or wet grass hill how far would the extra rear diff lock you really bring...
(If I remember well, Discovery’s were not equipped with diff locks anymore once Land Rover started using the traction control, around the millenium it was, but only a few years later they brought the diff locks back and until now kept them, so for sure it must have an added value, but not sure anymore how big it is with the current setup on the D5 as traction control becomes better and better).
If someone would go for a LR experience day, please ask this to the instructor, curious to know his/her answer/experience on this specific topic or yours of course!
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- Chopsy
- Member Since: 05 Jul 2018
- Location: Warwickshire
- Posts: 179
Every experience day car I've been in has had the additional rear locker. There seems to be a benefit if you are involved in serious regular off roading. I'm sure someone on here will better explain why, but I was told it stops the situation where one front wheel and one rear wheel spins simultaneously - perhaps opposite corners. The centre dif lock doesn't help but the rear one prevents this on rear axle basically giving better all round traction - or something like that...
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- teaman
- Member Since: 03 May 2019
- Location: Surrey
- Posts: 44
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Labbix that fits with my mental model as well. Have a locking rear diff will give you a lot more torque available to one wheel if the other gets stuck, and provide more momentum in tough terrain. Otherwise, yeah, traction control braking limits and reactionary nature of the system is a constraint of a rear open diff.
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- mordred1973
- Member Since: 08 Jan 2019
- Location: Northamptonshire
- Posts: 758
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anyone who is on the Facebook D5 group....Paul from Australia will be able to tell you exactly how the EDif works and its benefits...
Mine has it, and I very much doubt it will ever be of any benefit to me ;lol
2023 D300 Metropolitan, Hakuba Silver, Low Range, Solar screen, Deployable towbar, FBH, sidesteps.
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- aaddrryyss
- Member Since: 14 Oct 2019
- Location: Bucharest
- Posts: 3
On a Discovery3 that had no rear locker, I killed a pair of rear brake pads in 6000 Km.
More to the point, TerrainResponse did it.
And out of those 6000 km, I know of at least 50 muddy, crawly, miserable kilometers that I suspect had the greatest contribution. Those and a river crossing...
When back on tarmac, I had to waste 3 long hours taking each wheel off on the side of the road to clean the wheel wells and brake rotors (to the best of my limited, side_of_the_road ability).
In my experience, TerrainResponse works very, very hard to mimic a rear locker. It doesn't work equally hard on the front axle.
If given the opportunity to grab a D5 in the future, I'll make damn sure to get one with a rear locker.
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- DieselRanger
- Member Since: 12 Oct 2017
- Location: God's Country, Colorado
- Posts: 766
I don't have the rear diff lock and I can't personally imagine a scenario where I think I'd need it. I've been on steep climbs over rough, loose marble-to-bowling-ball sized rocks and gravel, I've been in deep snow and with three wheels on ice and one in a hole, I've been in sand and mud, and I've used all the TR2 modes. I have not seen a situation where finesse, some colorful language, low range and TR2 won't get you out of. Granted, a rear locker might get you out quicker and easier, but consider the cost and maintenance vs. the benefit.
I didn't get the rear locker as that would have meant I had to gain the 3rd row. I didn't want the 3rd row.
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- Labbix
- Member Since: 05 Mar 2018
- Location: Tanzania
- Posts: 955
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Hi DieselRanger, strange JLR combines it with the 3 row, here it is a separate option.
But what you think would be the extra cost for the diff lock (after purchase) when you know that replacement of the brakes might/will be quicker without the lock?
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- mordred1973
- Member Since: 08 Jan 2019
- Location: Northamptonshire
- Posts: 758
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mine has it, I very much doubt it'll ever be used in anger. However, you often hear/feel it in normal road driving.
2023 D300 Metropolitan, Hakuba Silver, Low Range, Solar screen, Deployable towbar, FBH, sidesteps.
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- DieselRanger
- Member Since: 12 Oct 2017
- Location: God's Country, Colorado
- Posts: 766
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Labbix wrote:
Hi DieselRanger, strange JLR combines it with the 3 row, here it is a separate option.
But what you think would be the extra cost for the diff lock (after purchase) when you know that replacement of the brakes might/will be quicker without the lock?
I've always been jealous of the ability to a la carte order almost any combination of options in vehicles over there - I was never able to take advantage of the special ordering benefits we got when we were stationed overseas when I was in the Air Force. You could pretty much custom-order any vehicle and have it shipped home for free.
As to the brakes, I think the brakes are going to wear faster from things like the cornering brake control that drags the inside rear brake in turns to help turn-in, as well as stability control to counter high crosswinds and trailering on road, versus wear in off-road situations where it has to brake a wheel that's spinning under little to no load for traction control. I think you'd have to do a lot of heavy off-roading to experience significant wear that way.
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- aaddrryyss
- Member Since: 14 Oct 2019
- Location: Bucharest
- Posts: 3
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DieselRanger wrote:
... versus wear in off-road situations where it has to brake a wheel that's spinning under little to no load for traction control. I think you'd have to do a lot of heavy off-roading to experience significant wear that way.
aaddrryyss wrote:
...killed a pair of rear brake pads in 6000 Km.
More to the point, TerrainResponse did it.
Well..."little to no load"...may or may not be so. I'm inclined to the latter. The brakes have to work equally hard on that wheel as the actual motive force that drive it's pair on the other side of the axle.
Also, keep in mind the possible contaminants...sand (including the wet variety), mud, grit...All this stuff has the potential to act like grinding paste.
I view a rear locker as an essential piece of gear. There would be plenty of opportunities (under my use cases) for it to be "used in anger", as someone expressed it. A third row of seats would be a very small price to pay, if they come bundled together.
I'm immensely grateful to those that spec their new cars with it, DON'T ever use it in anger and then part with the vehicle after 3 - 5 years or so, for half_to_a_third of the sticker price. 
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- Labbix
- Member Since: 05 Mar 2018
- Location: Tanzania
- Posts: 955
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Thank you all for this reflection, depending on the country we will be moving to I can at least make a better decision. I had it on my D4, not on my current D5 (but less off roading than with the D4), and will probably take it on my next D5. Even on very light off roading yesterday I saw the center diff lock is engaged quite often, assume it will be the same for the rear. And as I don’t really notice it when (partly) engaged, it might be better there to ease the drive if needed.
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- mordred1973
- Member Since: 08 Jan 2019
- Location: Northamptonshire
- Posts: 758
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The rear diff lock engages on the screen on a normal tarmac road away from a roundabout. So it would be pretty active on the soft stuff i guess. Obviously you cant control it the electronics does whatever it feels.
2023 D300 Metropolitan, Hakuba Silver, Low Range, Solar screen, Deployable towbar, FBH, sidesteps.
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- mordred1973
- Member Since: 08 Jan 2019
- Location: Northamptonshire
- Posts: 758
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'm immensely grateful to those that spec their new cars with it, DON'T ever use it in anger and then part with the vehicle after 3 - 5 years or so, for half_to_a_third of the sticker price.
Much braver man than me to want a D5 thats over 3 years old. Luckily i have a warranty until its 4 years, after which it'll be gone, not a chabce am i running it without a full warranty.
2023 D300 Metropolitan, Hakuba Silver, Low Range, Solar screen, Deployable towbar, FBH, sidesteps.
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- DieselRanger
- Member Since: 12 Oct 2017
- Location: God's Country, Colorado
- Posts: 766
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aaddrryyss wrote:
Well..."little to no load"...may or may not be so. I'm inclined to the latter. The brakes have to work equally hard on that wheel as the actual motive force that drive it's pair on the other side of the axle.
Also, keep in mind the possible contaminants...sand (including the wet variety), mud, grit...All this stuff has the potential to act like grinding paste.
I think LR's traction control is more intelligent than a mid-2K's pure viscous coupling. They reduce throttle and let the brake lock on the spinning wheel and then gradually let power back on once the traction has been established. Once the torque path is established it's not 1:1 power transfer left to right any more.
I still wager that unless you're climbing Ben Nevis on a daily basis the wear due to traction control and grit in off-road situations is going to be orders of magnitude less than the wear due to brake-biased cornering assistance and just keeping the big brute pointed straight in daily motorway driving, if only because of the ratio of time spent in one situation vs. the other.
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- harrythespider
- Member Since: 19 Jul 2018
- Location: cumbria
- Posts: 417
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I have the active rear diff, I was advised by the dealer to leave it set on auto, I can feel it engage on wet slippy roundabouts if being 'enthusiastic' but off road I cant say it is noticeable when engaging.
3.0 HSE. climate HUD active diff. elec towbar. FBH and timed climate.Capability plus pack.split TV. surround sound. Intelligent seating. adaptive lights, wade sensing. 360 cameras.pro pack.cooler.advanced tow, auto park,activity key+ more!!!!
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