All wheel drive vs 4 wheel drive vs ?

[one_iota]

So the Land Rover specs contain the following small print:

"1 Permanent All-Wheel Drive is standard on Land Rover Defender except for those fitted with new D200, D250 and D300 6-cylinder Diesel engines"

Can anyone here explain what that means and why it applies only to the diesel-engined variety?

Land Rover doesn't give any explanation as far as I can tell.

[ramblingboy42]

you have to get out and engage the locking hubs....simple

this gives you the opportunity to inspect the terrain that the all round cameras and sensors have already assessed.

[zilch]

So the Land Rover specs contain the following small print:

"1 Permanent All-Wheel Drive is standard on Land Rover Defender except for those fitted with new D200, D250 and D300 6-cylinder Diesel engines"

Can anyone here explain what that means and why it applies only to the diesel-engined variety?

Land Rover doesn't give any explanation as far as I can tell.

The D MHEV programmes can determine and disconnect the front wheels from the drive train if not required as far as i can remember,
uses some clutch pack, idea is to save you a minuscule amount of Diesel when on tarmac..and no doubt ensures Gerry Mc can
state he has green credentials

edited: Diagram added

171548

[zilch]

"Intelligent all wheel drive" is the phrase

[scarry]

More complications with very little up side.

[TB]

More complications with very little up side.

Yep. This is one of the reasons why when I suddenly found myself with the opportunity to change vehicles late last year I bought a 20MY vehicle in the wrong colour and with an unwanted sunroof from dealer stock rather than ordering a new build. The new driveline on the 6-cyl diesels is apparently a tiny smidge more fuel efficient but really seems like a step backwards in terms of driving four wheels with optimum traction.

Where the electronic centre diff has for a couple decades given us permanent AWD with automatic centre diff locking as needed, the new system is basically an automatic clutch version of the old 2H/4H and locking hubs arrangement. The only reason for doing it is to reduce spinning mass and friction losses in situations where RWD will suffice. Doesn't seem right for a Defender, especially a diesel one.

[rar110]

Ok does that mean all current model
Defender diesels are now intelligent (part time) FWD, and only the petrols non hybrid are full time FWD?

[one_iota]

Ok does that mean all current model
Defender diesels are now intelligent (part time) FWD, and only the petrols non hybrid are full time FWD?

That is how I read it.

It begs the question "why only diesels?"

If there are economies and emission reductions to be had albeit marginal why not also with the petrol engine?

[TB]

Ok does that mean all current model
Defender diesels are now intelligent (part time) FWD, and only the petrols non hybrid are full time FWD?

Depends what you mean by "FWD".

If your "F" means "Front", then no. The transfer case doesn't have a differential component any more, and the rear drive shaft is a permanent connection from the TC to the rear diff. The rear wheels are always driven. The centre clutch controls whether any drive is also given to the front, but remember there's no diff so it's a 1:1 ratio just like old-school 4WD mechanisms.

If your "F" means "Four" then yes.

[one_iota]

..and no doubt ensures Gerry Mc can
state he has green credentials



171548

I think what we are witnessing are the dying throws of the diesel engine given the emission control regulations being introduced particularly in Europe. Canada and the USA don't import the diesel-engined versions.

These are marginal gains from major engineering efforts. We are working beyond the Pareto principle.

[one_iota]

...... The transfer case doesn't have a differential component any more, and the rear drive shaft is a permanent connection from the TC to the rear diff. The rear wheels are always driven. The centre clutch controls whether any drive is also given to the front, but remember there's no diff so it's a 1:1 ratio just like old-school 4WD mechanisms.

That is not how I read the diagram that Zilch posted.

The clutch in the transfer case distributes drive to the front axle via the variable engagement of the plates acting as a differential. Torque is applied between 50/50 (1:1) rear to front and 100% rear to 0% front depending on demand. My view is that providing the system operates as programmed then there will be no practical difference between this and the traditional 4wd system that we are used to. The 4wd system we use currently is in reality only 1 wheel drive: 100% of torque goes to the wheel that has lost traction unless we lock the centre diff in which case 50% goes to that wheel making the vehicle 2wd. (Ignoring other traction aids like cross axle diff locks and TC)

This is how it operates in a Jaguar:

Intelligent Driveline Dynamics | Jaguar Owners | Intelligent driving technology (https://www.jaguar.in/ownership/all-wheel-drive/idd.html)

So I presume the Defender version is a development of that.

[TB]

OK we are probably reading it the same way but tripping over descriptions.

I'm saying that the rear drive shaft is permanently driven so that whenever the gearbox output is turning, so is the rear diff. The rear diff of course is still a differential and relies on either TC or the e-locker to manage slip when traction is uneven between left and right.

The front drive shaft default to not being driven. It requires a clutch to transfer torque from the TC or rear shaft (unclear technically which bit). However it's "1:1" in the sense that the front shaft and rear shaft cannot be driven at different speed other than if the clutch slips such that the front shaft goes *slower* than the rear. Now think about that for a sec. When do you ever have a situation where the front wheels should be spinning slower than the rears? Never. Front wheels need more speed than rears because their turning radius is larger. There's no centre differential function whatsoever and the clutch doesn't make up for that.

So it's like an automatic switch between RWD and traditional 4WD without the centre diff. Because it's automatic you don't have to get out and lock hub and you don't have to worry about wind-up etc.

The precursors to this that I've seen (eg Haldex) were all front-wheel-drive based with torque sent to the rear as needed. That makes much more sense from a clutch vs differential perspective.

[one_iota]

We are in furious agreement TB. [bigsmile]

[DiscoJeffster]

The engagement is 1:1 but the amount of torque delivered could be variable (don’t know if this system supports that). If torque was variable to the front it will give the Defender a far more dynamic driving style with a rear bias and only the right amount of torque to the front, reducing under steer which is the killer of most simple all wheel drive systems.

Sure it’s another thing to go wrong and wear out but they’re generally known to be extremely reliable systems.

[TB]

The engagement is 1:1 but the amount of torque delivered could be variable (don’t know if this system supports that). If torque was variable to the front it will give the Defender a far more dynamic driving style with a rear bias and only the right amount of torque to the front, reducing under steer which is the killer of most simple all wheel drive systems.

You gotta remember that without a centre differential, there's no way to drive the front shaft faster than the rear. That means this system makes understeer *worse*, just like it does in old-school part-time 4WD.

And because the rear is permanently driven, the only scenario where the front could be using more torque that the rear in this system is when the rear has lost traction and the front has all the grip.

[scarry]

If its used in the Defender to reduce fuel burn, then the front wheels would be programmed to only be used when absolutely necessary, one would presume.

In the Jag link in a previous post,there is no mention of fuel burn, just vehicle handling.

Interesting they also admit to looking at all the other manufacturers systems, which seems to point to them wanting to copy something another manufacturer has already designed and uses, but couldn't find anything that would suit their application,and what they wanted to do.

[one_iota]

...In the Jag link in a previous post,there is no mention of fuel burn, just vehicle handling.


I also find it interesting that JLR makes a big deal out of the Jaguar's system but is deathly quiet about that in the Defender. One reason might be that we long-term owners can be challenged by anything that wasn't in the Series 1 Land Rover [wink11]. We tend to be a bit luddite-ish and conservative.

[scarry]

I also find it interesting that JLR makes a big deal out of the Jaguar's system but is deathly quiet about that in the Defender. One reason might be that we long-term owners can be challenged by anything that wasn't in the Series 1 Land Rover [wink11]. We tend to be a bit luddite-ish and conservative.

It is advertised as a remote area go anywhere off road touring vehicle.
So adding more complications may put people off.

They did beat their chests about it having 85 PCB's,but that seems to have quietened down as well.

[rick130]

It looks like a Haldex type system that's been used in all wheel drives for years.
It drives well, relatively cheap to manufacture and torque can be apportioned to influence driving characteristics, ie. great on something like a Golf but IMO it's not a 'serious' 4wd system, where you sometimes need the driveline locked to proceed.

[one_iota]

I'd be interested to see the terrain response in comparison with the "non-intelligent" AWD system in the petrol version. Owners of the 2022 Diesel please step forward. [tonguewink]

The outstanding question is "why only the diesel?"

Do we have a contact in JLR engineering?

[Graeme]

"why only the diesel?"Likely to be to reduce driveline NVH when coupled with a diesel engine, but IMO inconsequential off sealed roads.

[one_iota]

Likely to be to reduce driveline NVH when coupled with a diesel engine, but IMO inconsequential off sealed roads.

Yes according to JLR this is one of the benefits.

The TLA "NVH" is?

I think I could guess but...

[one_iota]

It looks like a Haldex type system that's been used in all wheel drives for years.
It drives well, relatively cheap to manufacture and torque can be apportioned to influence driving characteristics, ie. great on something like a Golf but IMO it's not a 'serious' 4wd system, where you sometimes need the driveline locked to proceed.

According to the diagram above it can operate as locked front and rear albeit controlled by the JLR Intelligent Driveline Dynamics.

[JessicaTam]

Yes according to JLA this is one of the benefits.

The TLA "NVH" is?

I think I could guess but...
Noise, Vibration, Harshness. :)

Hopefully there is a setting where it can be left in 4wd. I would rather have 4wd/Awd all the time so no need to engage anything when driving in the rain or on a dirt road. I would take the extra traction over the (slight) loss of fuel economy anyday.

[one_iota]

Noise, Vibration, Harshness. :)

Hopefully there is a setting where it can be left in 4wd. I would rather have 4wd/Awd all the time so no need to engage anything when driving in the rain or on a dirt road. I would take the extra traction over the (slight) loss of fuel economy anyday.

The Disco 300 Tdi had a rubber joint in the driveline to deal with this...how far we have come!

I think that the system detects the traction conditions and engages the torque distribution accordingly...no need to engage anything. This is how the other defenders work it's just that this one works slightly differently. Add an E-diff and there will be another level of control albeit also responding autonomously.

[rar110]

A 2022 L663 is looking pretty unappealing.

[rar110]

Depends what you mean by "FWD".

If your "F" means "Front", then no. The transfer case doesn't have a differential component any more, and the rear drive shaft is a permanent connection from the TC to the rear diff. The rear wheels are always driven. The centre clutch controls whether any drive is also given to the front, but remember there's no diff so it's a 1:1 ratio just like old-school 4WD mechanisms.

If your "F" means "Four" then yes.

Thanks, yes meant 4WD not front wheel drive.

[DiscoJeffster]

You gotta remember that without a centre differential, there's no way to drive the front shaft faster than the rear. That means this system makes understeer *worse*, just like it does in old-school part-time 4WD.

And because the rear is permanently driven, the only scenario where the front could be using more torque that the rear in this system is when the rear has lost traction and the front has all the grip.

You have it backwards. Understeer comes from 4WD systems using a standard centre differential where torque is evenly split front to rear 50:50. Two problems occur. When the vehicle has excess torque applied - e.g. fast cornering with a foot-load of throttle, the front wheels which are trying to steer push wide as the torque they're trying to put the ground causes a outward slippage. This is exacerbated with the rear wheels also pushing the same torque forwards, driving the car off line.

In the system presented here (and note the diagram specifically calls out better driving dynamics), the rear wheels will drive the vehicle causing an effective yawing motion to improve the cornering. The front wheels are not trying to apply torque hence can focus on steering angle. This is why rear wheel drives are better around a track than a front wheel drive in any road car comparison. In the case where too much torque is applied to the rear wheels or the angle of the vehicle is off line, the front wheels can be engaged by the centre transfer case and apply small amounts of torque to bring the car back into line and improve overall traction.

This system is nearly identical to the Subaru STi which has a torque bias dial in the vehicle where you can specify how much bias you'd like in the system front to rear.

It's a clever system and I would not hesitate having it on my vehicle, but as I previously said, it is obviously another thing to go wrong, and expensive to repair I'm sure.

[rar110]

So more similar to the drive system in a discovery sport than a D4. [emoji15]

[one_iota]

A 2022 L663 is looking pretty unappealing.

I'm shifting to the positive!

I started this thread to find out more about the vehicle and in particular, get some clarity on the traction control system.

As always on AULRO there have been some interesting contributions here some of them on the mark and others speculative. After all, there are very few of these vehicles "on the road" here so information is thin and based on very little hard engineering. I wish JLR would be more open about this particular aspect: "Sell it to me!"

For me, if I make the move it will be at least 12 months away so plenty of time to get some "real world" perspectives. As I've said previously we Defender traditionalists are conservative and resistant to change. I think I'm up to the challenge.

[thumbsupbig]

[LyleC]

That is not how I read the diagram that Zilch posted.

The clutch in the transfer case distributes drive to the front axle via the variable engagement of the plates acting as a differential. Torque is applied between 50/50 (1:1) rear to front and 100% rear to 0% front depending on demand. My view is that providing the system operates as programmed then there will be no practical difference between this and the traditional 4wd system that we are used to. The 4wd system we use currently is in reality only 1 wheel drive: 100% of torque goes to the wheel that has lost traction unless we lock the centre diff in which case 50% goes to that wheel making the vehicle 2wd. (Ignoring other traction aids like cross axle diff locks and TC)

This is how it operates in a Jaguar:

Intelligent Driveline Dynamics | Jaguar Owners | Intelligent driving technology (https://www.jaguar.in/ownership/all-wheel-drive/idd.html)

So I presume the Defender version is a development of that.

I see in the Jaguar link it talks about the ability to go from 100% rear to 100% front drive, so maybe Defender has a simplified version of the Jag system?

[David Allen]

I'm shifting to the positive!

I started this thread to find out more about the vehicle and in particular, get some clarity on the traction control system.

As always on AULRO there have been some interesting contributions here some of them on the mark and others speculative. After all, there are very few of these vehicles "on the road" here so information is thin and based on very little hard engineering. I wish JLR would be more open about this particular aspect: "Sell it to me!"

For me, if I make the move it will be at least 12 months away so plenty of time to get some "real world" perspectives. As I've said previously we Defender traditionalists are conservative and resistant to change. I think I'm up to the challenge.

[thumbsupbig]

For years I have driven long hours across paddocks and open scrub. The centre diff makes a huge difference as wheels just climb over tussocks rather than bashing into them and fighting them via lack of power distribution in a centre locked tranmission (as is the case with every other 4wd on the market). Wheels can rotate and climb over tussocks (grass stumps) at different rates to avoid building up stress. It would be a pity to see Landrover abandon this advantage.

[TB]

You have it backwards.

Well... one of us now must, and it'll be interesting to try and figure out who! :)


Understeer comes from 4WD systems using a standard centre differential where torque is evenly split front to rear 50:50. Two problems occur. When the vehicle has excess torque applied - e.g. fast cornering with a foot-load of throttle, the front wheels which are trying to steer push wide as the torque they're trying to put the ground causes a outward slippage. This is exacerbated with the rear wheels also pushing the same torque forwards, driving the car off line.

Understeer comes from the front wheels losing traction, making them unable to apply a lateral force component to the front of the vehicle. Doesn't matter whether the front, rear or both axles are being driven, that's what understeer is. The difference between RWD and AWD (stick with open diffs and even splits for now) is that where a RWD's lateral steering force is entirely a component of the amount of grip (friction) the tyre can support *across* its contact patch, an AWD can add to that lateral force by applying rotational torque *along* the contact patch. What happens next is a product of many variables but boils down to AWD with open diffs giving you the potential for better steering performance provided you don't apply so much torque that you break front traction.

Spinning out the rears on a RWD is a whole different game and can be used to glorious effect. But I want to point out that in every scenario where we are turning successfully without any wheels losing traction, without understeer or oversteer, *the front wheels are spinning faster than the rear wheels*. They must, right? Because they're making a larger circle than the rears. This is why differentials exist at all.


In the system presented here (and note the diagram specifically calls out better driving dynamics), the rear wheels will drive the vehicle causing an effective yawing motion to improve the cornering. The front wheels are not trying to apply torque hence can focus on steering angle. This is why rear wheel drives are better around a track than a front wheel drive in any road car comparison. In the case where too much torque is applied to the rear wheels or the angle of the vehicle is off line, the front wheels can be engaged by the centre transfer case and apply small amounts of torque to bring the car back into line and improve overall traction.

First up, never believe marketing over engineering.

In the system presented here, the vehicle is shown is a variant of the old, old school 4WD. It's got a permanently driven rear shaft with 1:1 speed ratio from the TC. And it has a mechanism whereby the front drive can be nearly instantly connected and disconnected from the rear drive, with the same 1:1 ratio. And here's the key point: with this mechanism alone it's completely impossible to apply forward-driving torque to the front wheels during a turn, because without a centre diff there's no way for the front drive shaft to spin faster than the rear. In fact the opposite is true – if you engage the front drive during a turn you will force the front wheels to slow their spin below what is needed to keep pace with the turn, you will introduce a lateral force component *opposite* to the direction of turn, and you will contribute to understeer.

These are exactly the same reasons why traditional 4WD must be disengaged when driving on bitumen. The lack of a differential makes it unsuitable for use on high-grip road surfaces and reduces rather than enhances turning performance.


This system is nearly identical to the Subaru STi which has a torque bias dial in the vehicle where you can specify how much bias you'd like in the system front to rear.

It's NOTHING like the Subaru AWD system, which is and always has been based on having a centre differential.


It's a clever system and I would not hesitate having it on my vehicle, but as I previously said, it is obviously another thing to go wrong, and expensive to repair I'm sure.

I wouldn't be surprised if it's cheaper than the auto-locking centre diff it's replacing, though it does have two clutches (centre and front) instead of two. And for the kind of driving I came to love in my four years with the Disco 4... hell no I don't want to take the step backward to one of these things.

Ask yourself why the more on-road performance-oriented P400 and V8 Defenders are still using the older centre diff arrangement rather than this.

EDIT: I asked myself that too! Turns out Jaguar created this system in order to maintain RWD sports car experiences with an extra degree of "I can still move when it's icy and drift like a champ" thanks to judicious applications of torque to the front wheels. Now I'm still asking the same question but finding it puzzling from the opposite direction.

[TB]

I just watched a bunch of videos on the Jaguar IDD system. Learned three things:

1. When initially driving away it engages the clutches to pre-emptively avoid wheel slip, just like LR locking centre diff has done for twenty years

2. In all other cases, the front is only given torque when wheel slip is detected somewhere. Note this, they only give torque to the fronts during fast turns when rear wheel slip occurs, ie oversteer. That makes sense, because at that point it's fine for the front and rear drive shaft to be turning at the same speed. The fronts can be pulling around the corner while the rear is spinning, and this works a treat for opposite lock.

3. They also have traction control like terrain response and I think can do left/right torque vectoring by braking – again with the emphasis on the rear wheels.

I'm not saying it's a total piece of crap. I'm just saying that it's not what I want in a Defender, especially a diesel one. Would have made more sense to me to put this RWD sports car augmentation into the big petrol models and left the diesels to crawl sure-footed over every terrain they encounter especially when it's not bitumen.

[one_iota]

TB,

I understand that your Defender's centre diff locks in response to the loss of traction and delivers 50/50 front and rear that circumstance. Is this via a clutch pack like the rear E-diff?

If the Jaguars system responds to lack of traction in the rear when cornering hard would a similar system modified for off-road driving also respond to the loss of traction and transfer some of the drive to the front? It seems this apportionment according to the JLR info is between 0 and 100% of 50%.

[Graeme]

I like the torque that my 4.4 TDV8 L322's centre diff provides to the front wheels when cornering, pulling the front around the bend and especially noticeable uphill where lesser vehicles seem to always have to cut the corner on a particular corner. The centre diff clutch pack wouldn't be engaged at all but the drive afforded by the diff works well for the heavy vehicle.

[TB]

I understand that your Defender's centre diff locks in response to the loss of traction and delivers 50/50 front and rear that circumstance. Is this via a clutch pack like the rear E-diff?

If I'm not mistaken, the centre differential is a planetary type rather than the pinion type we see front and rear. But yes, it uses an electronically-controlled clutch pack, as does the optional rear locker even though it's on a different type of differential. This is the same system that's been available since at least the intro of the L319 Discovery 3 and L320 RRS.

50/50 is what I have when all wheels have grip and the diffs are *un*locked. That's one big difference from the new system, which is 100% rear drive until the clutch engages.

If a front wheel starts to spin in my Defender, without any lockers it would suck up 100% of the available torque and I wouldn't move. Locking the centre makes it like that diff doesn't exist, so suddenly 100% of torque is available at both front and rear diffs. Because that front wheel still has no traction, the front axle can't offer any forward progress but all that torque is also available at the rear and provided neither of those tyres breaks grip we just move.

The Jaguar system moves off from a standstill with the clutch pre-emptively locking the front and rear drive shafts together. The benefit there over RWD is that if a rear wheel breaks grip the front can still pull the vehicle forward. In that instance, that's how you get 100% of torque to the fronts – because the rear has lost traction but there's no differential function in the centre.

Both the drivelines we're talking about here will suffer the same fate when getting cross-axled, and both have the same remedy: use the rear locker if fitted, and/or apply brakes to the spinning wheels.

So they're functionally very similar when the need is to overcome one wheel's loss of traction. They differ greatly when all wheels have traction and you want to make a turn.


If the Jaguars system responds to lack of traction in the rear when cornering hard would a similar system modified for off-road driving also respond to the loss of traction and transfer some of the drive to the front? It seems this apportionment according to the JLR info is between 0 and 100% of 50%.

Like I said before, the only way you can get 100% to the front is when at least one of the rears have no grip. And when turning with the Jaguar system, putting ANY torque to the front requires rear wheel slip (not necessarily spin, just enough slip to account for the lack of an actual differential). Or if the rear has more traction, the front wheel must slip (understeer). That's because when turning the front wheels have further to travel than the rears. If you lock them together in a turn then either the fronts must skid forwards or the rears must spin out.

And repeating yet again... the centre clutch without a differential makes the Defender *exactly* like an old school 4WD when that clutch is engaged. It works. You'll still use traction control and rear diff locker to maintain progress when one or more wheels doesn't have grip. But it won't be quite as smooth and assured as what we've been used to for the past couple decades of Discovery and RR.

[DiscoJeffster]

The centre clutch isn’t just on off - it’s variable so as long as the electronics don’t call for a complete lock, you will still have slippage and variability front to rear that you get with a standard centre diff. I would be quite sure the drive dynamics takes steering angle into account and wouldn’t lock it completely during cornering even under a traction loss event causing poor dynamics when cornering. [emoji2369]

[TB]

The centre clutch isn’t just on off - it’s variable so as long as the electronics don’t call for a complete lock, you will still have slippage and variability front to rear that you get with a standard centre diff. I would be quite sure the drive dynamics takes steering angle into account and wouldn’t lock it completely during cornering even under a traction loss event causing poor dynamics when cornering. [emoji2369]

If you apply that clutch during cornering it will act as a brake on the front driveshaft, not an aid to propulsion. You're seeming to miss the point still that when in a turn with full traction the front wheels have to travel further and therefore faster than the rears. You simply cannot "apply torque" using only a clutch in this situation. Only partially applying it means you're braking it more gently and extracting energy from the front via friction in the clutch.

Only when the rears are spinning faster than the front can the clutch be applied to direct torque to the front during a turn. So, oversteer situations only. Great fun. If you're in a sports car. I bought a Defender.

[rar110]

I'm shifting to the positive!

I started this thread to find out more about the vehicle and in particular, get some clarity on the traction control system.

As always on AULRO there have been some interesting contributions here some of them on the mark and others speculative. After all, there are very few of these vehicles "on the road" here so information is thin and based on very little hard engineering. I wish JLR would be more open about this particular aspect: "Sell it to me!"

For me, if I make the move it will be at least 12 months away so plenty of time to get some "real world" perspectives. As I've said previously we Defender traditionalists are conservative and resistant to change. I think I'm up to the challenge.

[thumbsupbig]

Yes, unfortunately the JLR Australian Defender brochure has very little technical information, and even features a LHD vehicle on the cover!

[DiscoJeffster]

In your first section you said if the front is engaged in a turn when you have traction it will hinder progress. My point is if you have traction it won’t engage the front and the front will happily steer on its merry way.

I get your point though, which is that the old system worked just fine and for the purposes of an off-road vehicle, this is not required or desired.

[TB]

If you apply that clutch during cornering it will act as a brake on the front driveshaft, not an aid to propulsion. You're seeming to miss the point still that when in a turn with full traction the front wheels have to travel further and therefore faster than the rears. You simply cannot "apply torque" using only a clutch in this situation. Only partially applying it means you're braking it more gently and extracting energy from the front via friction in the clutch.

Only when the rears are spinning faster than the front can the clutch be applied to direct torque to the front during a turn. So, oversteer situations only. Great fun. If you're in a sports car. I bought a Defender.

Oh hey, new thought in the spirit of "yes, and..."

If we think about understeer, we can't just close the clutch and get more drive to the front because of the reasons I've already explained. But maybe, given that we're already sliding forwards on the front wheels, they can select which wheels are sliding and which are driving! If you lock the centre clutch, then apply just the right amount of brake to each of the inside wheels, you can make those inner wheels have all the skid action while the outer wheels get the exact right rotation speed for front/rear courtesy of the open diffs – and then you can drive both front and rear on the outside to help power around the corner.

You could do the same thing with a locking centre diff, by the way. But it's at least one way the clutch-only arrangement might actually make a positive contribution to a turn at speed.

[one_iota]

Like I said before, the only way you can get 100% to the front is when at least one of the rears have no grip. And when turning with the Jaguar system, putting ANY torque to the front requires rear wheel slip (not necessarily spin, just enough slip to account for the lack of an actual differential). Or if the rear has more traction, the front wheel must slip (understeer). That's because when turning the front wheels have further to travel than the rears. If you lock them together in a turn then either the fronts must skid forwards or the rears must spin out.



Let me be abundantly clear TB. No more than 50% will be delivered to the front, on that we agree. However this system delivers between 0 and 50% to the front depending on demand. It is in a sense is a limited-slip differential. I could imagine that when travelling in a straight line the front driveline is disengaged...the is no need for a differential. When turning there is a requirement to allow for differential rotation at least between front and rear. Could the variable torque distribution provided by the transfer case clutch plates provide this?

[CrustyNoodle]

I'm (mostly) with TB on this... A differential is very different from a clutch when it comes to distributing power. I think the point TB is making but doesn't seem to be being adopted is the fact that a differential will enable the output speed to be higher than the input speed. So if the input to the diff is turning at say 100 rpm, the rear could turn at 98 rpm but the front would turn at 102 rpm! This is fundamentally different from 50:50 torque split and is the whole point of a differential.

I'd say the new system will bias on-road performance by giving the car more of a rear wheel drive feel through the corners (as the fronts generally won't do anything other than actually brake the front axle when clutch is engaged). This "might" have a similar effect to left foot braking.

A couple of points though:

Clutch systems are reactive not proactive - LR admit this saying that it takes 0.15s to transfer from 100:0 to 50:50
I bet the clutch system on its own is cheaper than a center diff and clutch system



All that being said, bench racing doesn't prove anything, the real answers will come from the driving experience.
Either way, I wouldn't let the new system put me off the Dxxx Defenders - at least until proven otherwise.

[ramblingboy42]

I think you guys are going in a bit deep here.

The centre diff may aid understeer/oversteer but not control it

understeer/oversteer is controlled by suspension settings and tyre pressures

if you want to decrease your understeer increase your front tyre pressures or decrease your rear tyre pressures or conversely soften or harden your front/rear suspension or both

for some strange reason many here operate their vehicles with major front/rear tyre pressure differences which cooks up understeer.

no differential will compensate for that.

btw my Ranger is almost identical to a 130 (yes you guys hate hearing that) except for rear leafs and my front/rear tyre pressures are always the same.

[Graeme]

Either way, I wouldn't let the new system put me off the Dxxx Defenders - at least until proven otherwise.One shouldn't forget that LR removed the ability to lock the D2 centre diff, only to reinstate the facility a couple of years later.

[TB]

Let me be abundantly clear TB.

Wouldn't dream of stopping you.


No more than 50% will be delivered to the front, on that we agree.

Er... no, we don't [biggrin]
Both a locking differential and this new clutch can deliver up to 100% of torque to the front, when the rears have no traction.


However this system delivers between 0 and 50% to the front depending on demand.

True, when at least one wheel on both front and back still has traction.


It is in a sense is a limited-slip differential.

That's a real stretch, though I possibly understand what you're trying to get at. It's sorta, in a vague way, like half of an LSD, in that it has a way to react to the rear wheels spinning out and increase torque to the fronts when that happens.


I could imagine that when travelling in a straight line the front driveline is disengaged...the is no need for a differential.

Quite. That's the stated purpose of the design – to allow the front driveline to stop spinning, reducing friction and saving fuel.


When turning there is a requirement to allow for differential rotation at least between front and rear. Could the variable torque distribution provided by the transfer case clutch plates provide this?

Well, no, not in the slightest. The clutch does exactly the opposite: it acts to force the front shaft to go at the same speed as the rear. That right there is the specific bee that got in my bonnet and made me start asking WTF are they thinking.

[SBD4]

171548


...
Both a locking differential and this new clutch can deliver up to 100% of torque to the front, when the rears have no traction.


The documentation posted by Zilch says that "0-50/50-100 (% front rear)".

I read that to mean maximum of 50% can be applied to the front and a minimum of 50% to the rear. The rear will always be driven regardless of its state of traction with between 50-100% of torque. Likewise, 0-50% for the front.

If you're saying that, because the rears have no traction and the fronts do, 100% torque is "applied" to the front then, that's different. With 50/50 torque split the rear's are still being driven which they wouldn't be if no torque was being sent to them.

Did I read you right?

[TB]

SBD4

Yes, the 100% front torque scenario is when the rears have no traction. And yes, there is always a tiny fraction of torque used to overcome the inertia of the drivetrain and the wheel itself so that it's not strictly possible to have 100% go to the front but I chose to ignore that detail unless somebody brought it up because it doesn't help understand what the clutch mechanism is actually doing.

But, I would say no that's not a 50/50 split when you're in that situation. With the centre clutch locked, and assuming that the clutch itself doesn't slip, the final distribution of torque depends firstly on the traction at the wheels and secondly whatever the traction control system is doing with the brakes. The clutch plays no active role in controlling that split though, which I think might be the point you are making. The clutch can't make the vehicle a front-wheel-drive with the rears disconnected from the engine.

The "Engineering Explained" channel on YouTube has a number of videos on differentials and AWD systems which I found helpful in decoding the discussion around all this. I want to highlight, yet again, that apart from JLR a clutch system like this seems to only ever be used on a front-drive vehicle to recruit the rears for additional drive. That way around makes sense because the rear drive shaft would always be moving equal to or slower than the front, and so applying the clutch would always be an accelerating and never a braking force, and allows that application to be partial and progressive up to the 50/50 point. Flipping it around the other way it is largely reduced to being an on/off switch for old school 4WD. See if you can find a scenario where the Defender's rear drive shaft would be moving faster than the front, such that applying the centre clutch would allow a partial transfer of torque rather than an immediate 50/50 or 100/0 engagement.

Finally, that LR document that was shared here, while it contains some very useful information, was not released without marketing dept's stamp of approval. They made sure to convey the story they wanted people to hear in a way that encourages the emotions they want you to feel about the product. But if you just look at the bare facts of it: it's a clutch that can clamp the front driveshaft to the rear one so that instead of RWD you have 4WD. Work forwards from there rather than backwards from the marketing.

[Gregz]

Could JLR have changed the ratios in the front diff to make the front wheels rotate faster than the rear wheels, and then control the difference using the clutch ?

[TB]

Could JLR have changed the ratios in the front diff to make the front wheels rotate faster than the rear wheels, and then control the difference using the clutch ?

That's a damn good question, and something I wondered about myself.

"Control the difference" in practice just means accepting more clutch slipping, heating and wear in preference to tyre slip on the ground. It could certainly make for more sensible on-road high-range torque splits but I'm unsure whether it would be better or worse for low-range off-road contexts.

I wish JLR would give us some proper technical insight into what they've built.

[one_iota]

I wish JLR would give us some proper technical insight into what they've built.

Absolutely!

It is fundamental to answering the question I asked in the beginning. Until the engineering department at JLR puts its cards on the table apart from us seeing a vague diagram published on DEFENDER2.com then as they say "the jury is still out"

[Graeme]

Could JLR have changed the ratios in the front diff to make the front wheels rotate faster than the rear wheels, and then control the difference using the clutch ?
My guess is absolutely not! The old centre diff isn't "locked" unless driving in a straight line and I expect the LR have done the same with the new arrangement.

[Gregz]

This is from the MY21 RRS Press kit( seems slightly similar to the Defer to me, but I note the term "bevel gear centre differential", whatever that is, that might distinguish it from the Defer set-up)
Press kits for the Defer and Disco had even less info. :

Alongside the suite of electronic all-terrain technologies, the Range Rover Sport’s four-wheel-drive capability is managed by a transfer case design. This has a smart actuator in place of a separate motor and ECU, resulting in a 1.5kg weight reduction. It is controlled through a multi-plate clutch. Together with the bevel gear centre differential it provides a 50:50 torque split.
The clutch uses wheel slip information from a range of sensors to distribute torque evenly between all four wheels, while a ‘shift on the move’ system allows drivers to switch between high and low gears at up to 60km/h (37mph). The Active Rear Locking Differential can also be optimised for cornering stability and traction.

[TB]

A bevel gear differential is the traditional kind. Easy to discover with a quick web search.

[Sweetpea]

I am interested to know where this difference has been listed for the MY22 models. All I can see for engine selection is the same description regardless of the engine model selected which states (Automatic) All Wheel Drive in the online selector and in the downloaded selection information from landrover.com.au

Can someone provide a link which shows the original clarification
thanks

[DiscoJeffster]

My guess is absolutely not! The old centre diff isn't "locked" unless driving in a straight line and I expect the LR have done the same with the new arrangement.

Agree. They wouldn’t want to be slipping it for extended periods when they want it in the equivalent of “locked”.

[one_iota]

I am interested to know where this difference has been listed for the MY22 models. All I can see for engine selection is the same description regardless of the engine model selected which states (Automatic) All Wheel Drive in the online selector and in the downloaded selection information from landrover.com.au

Can someone provide a link which shows the original clarification
thanks

"It gets curiouser and curiouser" said Alice (in wonderland).

As the originator of this topic I raised it because when I did a "build you own" it came up as a footnote which I cut and pasted...so I went looking for it to answer your request.

Now it seems not to be the case. A rebuild doesn't declare this.

So what is going on? Is this a storm in a tea cup or JLR hiding something or did I dream it?

[TB]

The iGuide documentation for 22MY Defender includes a section on "All Wheel Drive (AWD)" that states:


The AWD system automatically varies the status between AWD and Rear Wheel Drive (RWD) to suit the current driving style and prevailing conditions.

RWD is only possible in the new driveline arrangement we've been discussing. So not a figment of your imagination.

[scarry]

So is it like old school,RWD,but FWD instead of operated by the driver with a lever,is operated by a clutch that is electric,signal coming from an ECU?
No center differential at all?

And driver cannot change from AWD to RWD,or visa versa,it is done automatically?
But driver can change different TR modes,and high and low range,that may determine when FWD occurs.

[one_iota]

The iGuide documentation for 22MY Defender includes a section on "All Wheel Drive (AWD)" that states:


RWD is only possible in the new driveline arrangement we've been discussing. So not a figment of your imagination.

I take it that this was from the downloadable Owners App.

I note that there is no distinction between petrol and diesel versions in the iGuide.

The new 2022 brochure describes all versions as AWD without qualification or distinction between petrol and diesel vehicles. It also doesn't describe AWD in detail.

So my take is that the 2022 Defender both diesel and petrol will have the same AWD system as described in the iGuide.

The footnote that I referred to in my opening post: "1 Permanent All-Wheel Drive is standard on Land Rover Defender except for those fitted with new D200, D250 and D300 6-cylinder Diesel engines" no longer exists in the sales documentation. In fact nowhere in any of the new documentation have I seen the term "permanent 4wd" used.

Buyers beware.

[B.S.F.]

What is the difference between the "New" system and the one used on the very first 80" Land Rovers between 48 and 51? I've tried to read all 7 pages of this thread but got more and more confused.
.W.

[TB]

So is it like old school,RWD,but FWD instead of operated by the driver with a lever,is operated by a clutch that is electric,signal coming from an ECU?
No center differential at all?

And driver cannot change from AWD to RWD,or visa versa,it is done automatically?
But driver can change different TR modes,and high and low range,that may determine when FWD occurs.

If by "FWD" you mean Four Wheel Drive rather than Front Wheel Drive, then yes that's pretty much how I see it.

[TB]

I take it that this was from the downloadable Owners App.

Yep.


I note that there is no distinction between petrol and diesel versions in the iGuide.

The new 2022 brochure describes all versions as AWD without qualification or distinction between petrol and diesel vehicles. It also doesn't describe AWD in detail.

So my take is that the 2022 Defender both diesel and petrol will have the same AWD system as described in the iGuide.

Yikes! You could be right about that.


The footnote that I referred to in my opening post: "1 Permanent All-Wheel Drive is standard on Land Rover Defender except for those fitted with new D200, D250 and D300 6-cylinder Diesel engines" no longer exists in the sales documentation. In fact nowhere in any of the new documentation have I seen the term "permanent 4wd" used.

Buyers beware.

I'm baffled. At least there's still a locking rear diff option, and Terrain Response is still the best on the market. And maybe the new system is somehow amazing in a way I just haven't yet come to understand. A big batch of new ones is getting delivered to Aussie customers this week so I'm looking forward to some first-hand reports.

[TB]

What is the difference between the "New" system and the one used on the very first 80" Land Rovers between 48 and 51? I've tried to read all 7 pages of this thread but got more and more confused.

That depends on what an "over-run freewheel unit" is. I can be sure it's not a computer-controlled clutch though.

Something purely mechanical that permits the front axle to be driven but also allows for that axle to spin faster than the rear during cornering almost sounds better than a clutch! The clunkiest option I can think of (literally) would be like a ratchet mechanism. Another would be a cam-based setup that increases friction in one direction but releases it in the other. Both of them would result in the the reverse gear being RWD only – is that what happens in those old LRs?

[scarry]

That depends on what an "over-run freewheel unit" is.

FWIW,the old man had a Rover 75 that had one of those,when initiated,it free wheels on overrun.No engine braking.

I was too young in those days to know how it worked,but it seemed to work well.

[B.S.F.]

That depends on what an "over-run freewheel unit" is. I can be sure it's not a computer-controlled clutch though. Something purely mechanical that permits the front axle to be driven but also allows for that axle to spin faster than the rear during cornering almost sounds better than a clutch! The clunkiest option I can think of (literally) would be like a ratchet mechanism. Another would be a cam-based setup that increases friction in one direction but releases it in the other. Both of them would result in the the reverse gear being RWD only – is that what happens in those old LRs?Yes, to reverse in four wheel drive you had to lock the two shafts together by pulling up a ring on the floor You described it pretty well. Funny how 70 years ago they managed to get a message across in a couple of sentences.
.W.

[Arapiles]

So more similar to the drive system in a discovery sport than a D4. [emoji15]

Well, look on the bright side - you can now buy a Freelander 2 and hand on heart say that it's just like a Defender.

[Graeme]

That depends on what an "over-run freewheel unit" is. I can be sure it's not a computer-controlled clutch though.One of my tractors has a free-wheeling sprag clutch in its 2nd gbox low gear, which has rollers that only grip in 1 direction. In the tractor it allows smooth down-shift, only engaging once the input shaft is driving the output shaft.

[TB]

One of my tractors has a free-wheeling sprag clutch in its 2nd gbox low gear, which has rollers that only grip in 1 direction. In the tractor it allows smooth down-shift, only engaging once the input shaft is driving the output shaft.

Very cool! Maybe LR has put a version of this into the new driveline and just forgotten to mention it. That would get me past the larger of my two objections to this new system.

[TB]

This statement is still in the fine print on The Land Rover Defender | Land Rover (https://www.landrover.com.au/vehicles/defender/index.html)

Permanent All Wheel Drive is standard on Land Rover Defender except for those fitted with new D200, D250 and D300 6-cylinder Diesel engines.

[one_iota]

This statement is still in the fine print on The Land Rover Defender | Land Rover (https://www.landrover.com.au/vehicles/defender/index.html)

Thanks, TB.

I've sent an email to JLR (Australia) seeking clarification.

Silence might be the reply but we shall see.

[one_iota]

Thanks, TB.

I've sent an email to JLR (Australia) seeking clarification.

Silence might be the reply but we shall see.

I have been advised by a Land Rover sales consultant after a few emails and a phone conversation that the AWD system as described in the iGuide applies to all 2022 Defenders regardless of whether the engine is petrol or diesel.

[TB]

I have been advised by a Land Rover sales consultant after a few emails and a phone conversation that the AWD system as described in the iGuide applies to all 2022 Defenders regardless of whether the engine is petrol or diesel.

How much do you trust the sales consultant? That directly contradicts information on the Australian web site where 6-cyl diesels are excluded from the “Permanent All-Wheel-Drive” claim via fine print, and on the US site which doesn’t have diesels and simply says “Permanent All-Wheel-Drive” without any disclaimers.

What a balls-up.

[one_iota]

TB,

Whether I trust LR Sales consultants or not is irrelevant.

I'm reporting back what I've managed to find out as I undertook to do.

As I said before: caveat emptor. That still stands.

Until someone bothers to find out more this is where this issue stands.

[DiscoJeffster]

At the end of the day, when you select an off-road mode it’ll more than likely lock the centre haldex clutch providing 50:50 and then use the traction system to maintain forward momentum, so when it matters it’ll work just fine.

[one_iota]

How much do you trust the sales consultant? That directly contradicts information on the Australian web site where 6-cyl diesels are excluded from the “Permanent All-Wheel-Drive” claim via fine print, and on the US site which doesn’t have diesels and simply says “Permanent All-Wheel-Drive” without any disclaimers.

What a balls-up.

The South African LR site makes no distinction between diesel and petrol. And does not use the term "permanent" before AWD.

It's worth commenting that the difference between various sites (theirs and ours) is significant. One possibility is that the responsibility for each site has been left to local production. This is risky from an editorial point of view. Things can change at a higher level without that being translated to the individual sites.

[one_iota]

I've received an emailed reply from another dealership which says and I quote in part: "Permanent all wheel drive with Twin speed transfer box and terrain response is standard on all Defenders".

So I repeat: buyer beware.



TB,

Whether I trust LR Sales consultants or not is irrelevant.

I'm reporting back what I've managed to find out as I undertook to do.

As I said before: caveat emptor. That still stands.

Until someone bothers to find out more this is where this issue stands.

[TB]

I've received an emailed reply from another dealership which says and I quote in part: "Permanent all wheel drive with Twin speed transfer box and terrain response is standard on all Defenders".

So I repeat: buyer beware.

Send 'em a copy of this error message that a few people have posted on FB and ask how this is possible on "permanent all wheel drive".

172484

[one_iota]

Send 'em a copy of this error message that a few people have posted on FB and ask how this is possible on "permanent all wheel drive".

172484

Thanks TB. Your devil's advocacy is helpful.

Given that two dealerships have offered contradictory advice I can now escalate this to JLR Australia Head Office to demonstrate that, at best, its dealerships don't know the product they are selling!

Stay tuned.

[JessicaTam]

The following is from the current UK Defender brochure:


ALL WHEEL DRIVE (AWD)
Compelling performance. Off and on road. The system intuitively controls the torque distribution between the front and rear axle. On challenging surfaces, such as sand, grass or snow, torque can be balanced between the front and rear wheels to maximise traction. In extreme conditions, where the front or rear wheels lose traction, 100 percent of engine torque can be distributed to the opposite axle for optimum grip. Our Intelligent AWD System* takes this even further
by allowing variable torque distribution, resulting in a more precise and dynamic on-road performance and higher torque capacity – all without sacrificing any of Defender’s inherent off-road capability.


*D200, D250 and D300 6-cylinder Diesels only.

Which is what I would expect. It has been a long time since I drove a 4WD that sent drive to wheels without traction.

LR are just doing it slightly differently than the usual traction control method of distributing torque.

[one_iota]

The following is from the current UK Defender brochure:


Which is what I would expect. It has been a long time since I drove a 4WD that sent drive to wheels without traction.

LR are just doing it slightly differently than the usual traction control method of distributing torque.

Yes I shouldn't be distracted by my current crusade, namely, bringing JLR to account with regards to its sales pitch.

My original question also seeks to understand the real-world ramifications of the engineering decision that has been taken by JLR. So far we are dealing with "black box" not "open source". That concerns me as much as anything else.

I'm keen to get feedback on the performance on and off road of the AWD system from users.

[one_iota]

Thanks TB. Your devil's advocacy is helpful.

Given that two dealerships have offered contradictory advice I can now escalate this to JLR Australia Head Office to demonstrate that, at best, its dealerships don't know the product they are selling!

Stay tuned.

I've had a positive response from Head Office to its credit. It has been formally raised as an issue to be resolved. (It even has a number!)

[TB]

Translation from marketing-speak:

Compelling performance. Off and on road.
"This is a Land Rover that's nice to drive."


The system intuitively controls the torque distribution between the front and rear axle. On challenging surfaces, such as sand, grass or snow, torque can be balanced between the front and rear wheels to maximise traction. In extreme conditions, where the front or rear wheels lose traction, 100 percent of engine torque can be distributed to the opposite axle for optimum grip.
"We do real 4WD systems, not a dinky AWD that can't deal with a bit of wheel slip."


Our Intelligent AWD System* takes this even further by allowing variable torque distribution, resulting in a more precise and dynamic on-road performance and higher torque capacity – all without sacrificing any of Defender’s inherent off-road capability.
"We've done something weird and hard to explain on the new diesels, but trust us it's awesome! When you're off-road it's sorta like an old Series LR except instead of having to pick between 2WD and 4WD the computer can kinda blend in between them when it thinks the front wheels need to help you along. And on-road it's like our cool Jag sports cars (because that's the same system we've put in here)!"


LR are just doing it slightly differently than the usual traction control method of distributing torque.

Slight disagree here. Terrain Response's traction control software is still doing left/right torque management via braking on the front axle and also on the rear if you have the open diff there. If you have the rear locking diff then you get "torque vectoring by braking" on the rear to assist with turns also (this is actually awesome off-road and I don't think it gets called out enough). Those statements apply to both the familiar permanent AWD system with the centre locking diff and the new Jag-sourced system with the clutch-only connection for the front drive shaft. It's those transfer case mechanisms, not traction control, that are responsible for front/rear torque management.

[TB]

Couple of updated thoughts from me.

First thanks for the discussion. I didn't dive into this with an aim to make trouble, I do it to try and understand things that LR's own materials do a **** job of explaining. As we've worked through it over time I actually feel more relaxed about the new system because my initial questions have gradually found reasonable answers.

The words "higher torque capacity" from JessicaTam's post just now are potentially important. The new diesels are pretty torquey. Maybe the old locking centre diff finds it hard to cope? Maybe a big clutch taking up the available space can more reliably direct all that torque to the front when needed? That would be a clear engineering benefit of the new system.

Learning that this system comes from the Jaguar side also helps understand the way it's tuned, and this will be particularly relevant on fast dirt and gravel, even some bitumen. I think the permanent AWD via a centre diff is probably still better in terms of overall traction... though perhaps not by much. But I have no doubt the Jag system would be more fun, because it's literally designed to pull you through corners in oversteer!

And off road it's got all the capability of "part-time 4WD" systems (which is to say, a lot) plus the flexibility to relax the front drive while turning if rear traction isn't a problem.

So: slightly improved fuel economy, potentially better handling of high torque engines, likely more fun on the twisty bits... in exchange for losing a little bit of sure-footedness and possibly increasing tyre wear.

Like Mr Iota, I'm looking forward to hearing from owners of I6 diesels how their new Defenders go. Enjoy!

[Graeme]

The words "higher torque capacity" from JessicaTam's post just now are potentially important. The new diesels are pretty torquey. Maybe the old locking centre diff finds it hard to cope? Maybe a big clutch taking up the available space can more reliably direct all that torque to the front when needed? That would be a clear engineering benefit of the new system
Could be to reduce torque-steer.

[one_iota]

I've had a positive response from Head Office to its credit. It has been formally raised as an issue to be resolved. (It even has a number!)

I have received a reply from JLR Australia's Customer Relations Centre and I quote the substance of that reply.


Regarding your question on the AWD system, the footnote mentioned is correct and is relevant to Diesel powertrains which is D200, D250 and D300.

These have the intelligent driveline and offer a variable torque split front to rear.


The system can vary the distribution of the front/rear torque split, continuously monitoring the environment and driver inputs to optimise capability, composure, and efficiency.The new driveline can reduce driveline losses by 30% and improve CO2 emissions by more than 4 g/km while the ability to vary the torque split front to rear also supports optimised on-road handling and driving dynamics.

Typically, the system will vary the torque distribution from Rear to Front for efficient operation up to 50:50 when traction is a priority. The control is monitoring steering, vehicle acceleration and wheel speeds to optimise the response of the vehicle for the prevailing terrain to improve vehicle composure and reduce driver workload. For more extreme off-road driving such as rock crawl the centre coupling is locked to transmit more of the drive torque to the axle with the most available traction.

The control is linked to the vehicle Terrain Response functions and is designed to replicate the torque distribution of the existing driveline when traction is compromised.


In addition, the system has a gradient sensing function to ensure optimum torque distribution when descending steep slopes off-throttle to enhance Hill Descent Control performance.

The system has been engineered and tested to the same rigorous standards applied to all Land Rover drivelines and delivers customary Defender capability with enhanced efficiency.

[TB]

I have received a reply from JLR Australia's Customer Relations Centre and I quote the substance of that reply.

Good stuff - thanks!

Activating my marketing-speak decoder...


Regarding your question on the AWD system, the footnote mentioned is correct and is relevant to Diesel powertrains which is D200, D250 and D300. These have the intelligent driveline and offer a variable torque split front to rear.

The new diesels don't have a centre diff any more.


The system can vary the distribution of the front/rear torque split

The front wheels aren't always driven.


continuously monitoring the environment and driver inputs to optimise capability, composure, and efficiency.

But it's not a dumb part-time 4WD either. The Terrain Response computer decides when the drive the front wheels just like the earlier system decided when to lock the centre diff.


The new driveline can reduce driveline losses by 30% and improve CO2 emissions by more than 4 g/km

The latest emissions standards are really fricking tough to meet and we're chasing down every damn g/km.


while the ability to vary the torque split front to rear also supports optimised on-road handling and driving dynamics.

Oversteer is fun! We can do it deliberately now!


Typically, the system will vary the torque distribution from Rear to Front for efficient operation up to 50:50 when traction is a priority.

RWD when we can get away with it, only driving the front wheels when we have to.


The control is monitoring steering, vehicle acceleration and wheel speeds to optimise the response of the vehicle for the prevailing terrain to improve vehicle composure and reduce driver workload. For more extreme off-road driving such as rock crawl the centre coupling is locked to transmit more of the drive torque to the axle with the most available traction.

We have a 4WD function that works in the usual way.


The control is linked to the vehicle Terrain Response functions and is designed to replicate the torque distribution of the existing driveline when traction is compromised.

We don't trust the market to understand what we've done so we're doing a lot of hand waving and trying to reassure you that you won't notice any difference. Except for the oversteer bit – which is awesome right!?


In addition, the system has a gradient sensing function to ensure optimum torque distribution when descending steep slopes off-throttle to enhance Hill Descent Control performance.

We even remembered that the front wheels need to be connected to the engine for engine braking to work well downhill.


The system has been engineered and tested to the same rigorous standards applied to all Land Rover drivelines and delivers customary Defender capability with enhanced efficiency.

Please stop asking questions. It's a Land Rover. We can sell it because we snuck the CO2 emissions below the Euro limit and we really hope you'll be satisfied with all these superlatives.

[TB]

Now that these vehicles are arriving in people's garages we've learned some things, and one of those is something we should make sure everybody understands for safety reasons.

When a six-cylinder diesel Defender is parked, the front wheels are independent and unrestrained. The front driveshaft is disconnected from the rear, the right front wheel is disconnected from the front differential, and there are no parking brakes on the front.

So you are 100% relying on the rear wheels to prevent any rolling or sliding. The rear wheels are permanently connected to each other and the transmission via the rear differential so they have both the gearbox parking pawl and the park brakes restraining them.

The safety factor here is related to parking on any steep or slippery incline, and to jacking the vehicle up. Unlike all other modern LRs with permanent AWD, or older LRs with 4WD engaged, when you jack up a corner on one of these six-cylinder diesel Defenders you will not have the three other corners preventing movement: you will have only the rear wheels and potentially just one of them if it's a rear corner that you've lifted. If you lift a front corner you'll be able to spin that wheel freely.

It would be a very good idea for owners of these vehicles to add some sturdy wheel chocks to their kit.

[100inch]

Now that these vehicles are arriving in people's garages we've learned some things, and one of those is something we should make sure everybody understands for safety reasons.

When a six-cylinder diesel Defender is parked, the front wheels are independent and unrestrained. The front driveshaft is disconnected from the rear, the right front wheel is disconnected from the front differential, and there are no parking brakes on the front.

So you are 100% relying on the rear wheels to prevent any rolling or sliding. The rear wheels are permanently connected to each other and the transmission via the rear differential so they have both the gearbox parking pawl and the park brakes restraining them.

The safety factor here is related to parking on any steep or slippery incline, and to jacking the vehicle up. Unlike all other modern LRs with permanent AWD, or older LRs with 4WD engaged, when you jack up a corner on one of these six-cylinder diesel Defenders you will not have the three other corners preventing movement: you will have only the rear wheels and potentially just one of them if it's a rear corner that you've lifted. If you lift a front corner you'll be able to spin that wheel freely.

It would be a very good idea for owners of these vehicles to add some sturdy wheel chocks to their kit.
You are correct, but I wonder how many people were aware of the same safety issue with their classic RR's and Defenders. There was a reason LR packed a wheel chock with the tool kit. m

[one_iota]

Now that these vehicles are arriving in people's garages we've learned some things, and one of those is something we should make sure everybody understands for safety reasons.

When a six-cylinder diesel Defender is parked, the front wheels are independent and unrestrained. The front driveshaft is disconnected from the rear, the right front wheel is disconnected from the front differential, and there are no parking brakes on the front.

.....snip....

It would be a very good idea for owners of these vehicles to add some sturdy wheel chocks to their kit.


My Defender has a drum brake on the rear driveshaft. As I understand it, if the centre diff is not locked only the rear wheels are braked and so when a rear wheel is lifted the hand brake doesn't work. A chock was provided.

How does the parking brake system work in yours TB?

[cjc_td5]

My Defender has a drum brake on the rear driveshaft. As I understand it, if the centre diff is not locked only the rear wheels are braked and so when a rear wheel is lifted the hand brake doesn't work. A chock was provided.

How does the parking brake system work in yours TB?Technically, only the rear tailshaft is locked when the handbrake is applied. It is still possible for the rear wheels to spin in opposite directions through the rear diff centre. If jacking a rear wheel, engage the centre diff lock so the front axle becomes braked also.

[TB]

My Defender has a drum brake on the rear driveshaft. As I understand it, if the centre diff is not locked only the rear wheels are braked and so when a rear wheel is lifted the hand brake doesn't work. A chock was provided.

How does the parking brake system work in yours TB?

It's the modern style with a motorised gear on each rear wheel to clamp the brake closed. So each rear wheel gets independently held.

[101RRS]

Technically, only the rear tailshaft is locked when the handbrake is applied. It is still possible for the rear wheels to spin in opposite directions through the rear diff centre.

I have this happen to me in a series 3 parked on a steep concrete driveway with a 2 tonne trailer on the back. In gear (not 4wd) and handbrake on and holding - vehicle slowly slid down the drive with the rear wheels turning in opposite directions leaving rubber down the drive - was like watching in slow motion as it was so slow but it kept on going until I jumped in and applied the brakes.

[one_iota]

It's the modern style with a motorised gear on each rear wheel to clamp the brake closed. So each rear wheel gets independently held.

The entertaining and informative Simon Jefferson takes us on a discovery tour of the underside of his....the parking brake component is pointed out in passing.

New 2020 Defender Underbody Tour + Review Using Low Ratio + Off Road Mode - YouTube (https://youtu.be/XAsi_xSfkY4)

[TB]

An update on the situation with the 6-cyl diesels' driveline being in 2WD when parked...

Andrew from TuffAnt did some pretty thorough testing with his D300 and confirmed that this is the case when the TR mode is set to Comfort (the default) or Eco. The front wheels are completely unrestrained when the engine is off and the park brake applied.

However when you select any of the off-road modes (tested GGS, Mud Ruts, Sand and Rock Crawl, but not known about Wade) if that mode is selected when you turn off the vehicle then the front driveline clutches appear to remain locked. This is equivalent to having a locked centre diff but is still an open front diff.

Definitely an improvement and something all owners of those vehicles should be mindful of.

[Vin60]

Hi Everyone! Thank you for awesome tread. I presume, since we know D3.0 uses IDD, attached description of IDD transfer case is correct for D3.0 as well. However since Jaguar IDD uses permanent AWD system with standard 90% rear and 10% front torque, dynamically distributing it by IDD when needed and D3.0 has PWD, and needs to engage 2 clutches before IDD comes in force, it makes this system further more complicated then usual Juaguar transfer box - that's where all these "2WD drive only" mistakes come from. Also torque distribution should take longer them 100 ms quoted by Jaguar IDD. Not saying about possible steering problems when front wheels can not move quicker then rear wheels with AWD engaged. I see the only way, they could somehow avoid it is disconnect front axle when from wheels need faster spin then rear one. However JLR does not state D3.0 operates like rear wheel car in turns but instead they insist it works like proper AWD, i.e. no difference with D2.0 and Gas versions. That puzzles me out.

[Peterma]

Hi,
I own a defender L663 D300 and have had the time so far to play off road with it (about 17000km off road now, 19,000 on road). The vehicle does a lot of things that are simply not explained to us when we buy it. When doing the old coach road in North QLD, I learned that your more there for the ride than actually worried about how it does it or how to do it. It plays tricks with the drive train and suspension. Also if you jack it up and have all 4 wheels of the ground and spin the wheels fast enough it disengages the front when I estimated it was doing just over 20km/hr (if it was on the ground). I also learned that the suspension moves weight around to compensate when needed. I have experienced this. BTW very disconcerting when the vehicle takes control and you are ignored (breaks and accelerator(brown stain moment)). How is all of this is done LR seems to be keeping close their chest and I would too. What blew me away when dropping over 1m dropoff or driving up it, it makes it so effortless. I have quickly learned that comfort mode is good 99% of the time.

I think when Richard Hammond described it as an off road super computer, he was right. I am now convinced it will go where ever you reasonably want to and in so much comfort. Are there bugs in the software?, you bet, but I have just placed an order for a 3rd.

[Tins]

Hi,
I own a defender L663 D300 and have had the time so far to play off road with it (about 17000km off road now, 19,000 on road). The vehicle does a lot of things that are simply not explained to us when we buy it. When doing the old coach road in North QLD, I learned that your more there for the ride than actually worried about how it does it or how to do it. It plays tricks with the drive train and suspension. Also if you jack it up and have all 4 wheels of the ground and spin the wheels fast enough it disengages the front when I estimated it was doing just over 20km/hr (if it was on the ground). I also learned that the suspension moves weight around to compensate when needed. I have experienced this. BTW very disconcerting when the vehicle takes control and you are ignored (breaks and accelerator(brown stain moment)). How is all of this is done LR seems to be keeping close their chest and I would too. What blew me away when dropping over 1m dropoff or driving up it, it makes it so effortless. I have quickly learned that comfort mode is good 99% of the time.

I think when Richard Hammond described it as an off road super computer, he was right. I am now convinced it will go where ever you reasonably want to and in so much comfort. Are there bugs in the software?, you bet, but I have just placed an order for a 3rd.

All you need now is a robot behind the wheel. Let it have the fun.