Hello all,
This is my first post on this forum. I am a former owner of both a Discovery II and an LR4, both of which saw considerable time off road. Now I am considering a 2020 Discovery, and I've been trying to find out information about the mechanicals. I have found little on the website, but I did download the brochure PDF in which two terms are used: Permanent 4WD and (in the specs) all wheel drive. The meaning of "all wheel drive" seems to be a bit of a moving target, and changes depending on who's using it. Most of the time AWD refers to a primarily front-wheel-drive car with a Haldex rear differential (or similar) that will mete out a little power to the rear axle as needed. The Discovery Sport works like this, as do many Audis, the Volvo XC-90, etc.

So how does the Discovery driveline work? Can anyone supply any details please?
Thanks in advance . . .

 

The Discovery 5 is permanent 4wd with a 50:50 torque distribution and locking center diff. Plus a two speed transfer case.
It’s nothing like Haldex.
Power is always going to the front and rear axles equally, unless both front or both rear wheels start to slip at which point the system will automatically lock the center diff. In fact it can also partially lock the center diff it wants to, very sophisticated.
Traction is also maintained by using the wheel speed sensors and applying the brakes to any slipping wheel to direct power to the opposite side of the axle. Unlike previous Discoveries the system samples at a higher rate and is able to detect slippage in something like 6degrees of wheel rotation as opposed to much larger angles or even a full rotation (so you don’t see it scrabble much at all vs the old models).
If you get the optional rear locking diff it can also engage that (including partially) for even better performance.
Finally, it also monitors steering angle input, suspension travel and more to further improve its traction decisions.
Throw in the 900mm water wading (which as I understand it takes in water in chambers in the doors to stop the car otherwise floating), and very competitive approach, break over and departure angles due to the air suspension (make sure you get the air suspension) and ground clearance and you’re on a high tech winner...

 

I know there are other more capable vehicles out there in the market but don’t under estimate the DiscoV capabilities. I’ve learned so much during a Land Rover Owners’ event. Great way to learn the features and capabilities of the vehicle in a controlled setting.

 

Hi LoneStar. Thanks for your reply.
I'm relieved to hear that the Disco 5 is permanent 4WD. When I read the literature, and it described the vehicle as all wheel drive, with unibody construction, and full independent suspension, well, that starts to sound a lot like a crossover. Partially locking center diff? By what means does the center diff partially lock?
I guess the the question is: Is six degrees of rotation quick enough to prevent loss of momentum . . .
Can the locking diffs be engaged proactively by the driver, or does the car decide when to engage them?

That was a cool bit about the ballast tanks in the doors so the car doesn't wash away in deep water.

 

My wife and I were fortunate enough to attend a "Land Rover Experience" event at Quail Lodge in California. It was loads of fun. That was back in the Discovery II days. :-D


ETA: LoneStar I made a separate reply to you but it is being held up for moderation. Funny. I didn't include any curse words. I'll re-reply to you if my reply doesn't show up.

 

LoneStar, thanks for the reply. I'm glad to hear that the Discovery 5 has permanent 4-wheel-drive and a high-low transfer case. When I read in the literature the term all wheel drive, combined with unibody construction and independent suspension - well that sounds a lot like we're in Crossover territory along with the Volvo XC-90 and the 4-Motion VWs. But I'll take your word for it that it isn't. That said, when you mention that the center and rear locking differentials can partially lock - if we are talking about viscous couplings/clutch packs, I hate to say it but that sounds a lot like a Haldex. I would be very interested to know whether the driver can proactively lock the differentials, or if they can only be automatically locked by the terrain system. And if the latter is the case, and as you say, the ABS-based traction control is very responsive, then why aren't the locking diffs totally redundant?

Thanks for your patience. I'm not trying to bash the Discovery at all. I just want to know how it works, and am surprised to find that information is elusive.

 

Hey, nice ride! Looks like you are running Toyo Open Country AT(III?). What size tires are you running, and did you add a lift?

 

Don’t confuse the center diff locking and unlocking (even partially) to be like Haldex.
AFAIK Haldex sends power primarily to the front wheels and moves some power to the rear as needed, ie if the front begins to slip.

In normal driving the Discovery always sends power 50:50 to the front and rear wheels. Even when there is no slip. The locking of the center diff, with the ability to do so partially (unlike say a Jeep Wrangler where engaging 4 wheel drive vs 2 wheel drive means the front and rears are locked essentially, although the term isn’t quite accurate as the Wrangler doesn’t have a center diff) is what happens when the Disco starts sensing slip at either the front or back and allows it to move power distribution from the normal 50:50 front:rear to whatever ratio the slipping axle will allow.
The brake based system then allows it to deal with slippage from left to right side.
Is a locking (again electronic and partial capable) rear diff strictly necessary in addition to the brake based system. Not really. In many off road situations you have no need of a locking rear diff (like sand or mud) but for situations like rock crawling it really helps and stops the brakes from overheating and also causes less “scrabbling”. Although the driver can’t flick switches to turn the locking off and on, if you put it in day rock crawl mode, if you have a rear locker it will lock it. And as you’d likely be in rock crawl mode already if you were rock crawling and thus needed to manually lock the rear diff, well, it is already.
Not saying some extreme off roading expert may do better under manual control, but for most people the computer system is smarter and faster reacting and the ability to partially lock up makes turning a lot easier. Not to mention avoiding you forgetting to engage the locker or forgetting to disengage it.

 

You may find this video interesting:


They are using a Range Rover Sport here which is the same "premium" platform as the full sized Range Rover and the Discovery 5.
However of the three the Discovery V is the most capable off-road due to a combination of ground clearance, wading depth and so on. Therefore the Sport you're watching is not quite as capable but that hardly seems to matter in this test.
Note that they don't even put it in mud/ruts or rock crawl mode or whatever, they just leave it in auto, but you can still see the difference in traction it has vs the other premium SUV's, like the Volvo which I believe uses Haldex.

 

I am showing this video to my wife next time she starts talking about the Volvo XC90 T8. I am just happy she has a dislike of BMW and Mercedes.

Regarding the winter tires used in the test. Due to the pandemic I kept winter Nokians on our Mazda CX5 through the summer since we are likely to part ways with it soon, and I have been surprised by how little the tires have worn with local daily driving. It must not get hot enough in Seattle to affect them. We only had a hand full of days in the 90s this summer.

Seeing how well they held up made me think to go with all-weather Nokians year round for the Disco instead of seasonal switches between all-season/winter tires. I know some of you might laugh at winter tires on a 4x4, but I would say a lot of you live in Texas! Anyways, the all-weather Nokians I wanted are not available in 255/55/20 so I am going with the Toyo Open Country A/T IIIs as a year round tire. I am a bit weary about A/Ts with the snow-flake symbol since I assume they barely meet the requirement but I will give them a shot. I am having the Toyos put on today and the mountains passes around use are getting feet of snow as I type so I will find out soon if they are good enough.