All wheel drive vs 4 wheel drive vs ?

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Originally Posted by one_iota

"why only the diesel?"

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

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Originally Posted by Graeme

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

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Yes according to JLR this is one of the benefits.

The TLA "NVH" is?

I think I could guess but...

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Originally Posted by 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.

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

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Originally Posted by one_iota

Yes according to JLA this is one of the benefits.

The TLA "NVH" is?

I think I could guess but...

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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.

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Originally Posted by JessicaTam

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.

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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.

A 2022 L663 is looking pretty unappealing.

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Originally Posted by TB

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.

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Thanks, yes meant 4WD not front wheel drive.

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Originally Posted by TB

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.

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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.

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

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Originally Posted by rar110

A 2022 L663 is looking pretty unappealing.

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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]