D4 Rollover

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Originally Posted by LRD414

Thinking back as best I can and as you say it all happens fast with poor recall ....
But everything you've said here lines up and makes sense.
I do generally use Mud/Ruts majority of the time but thought Rock Crawl for this rock to reduce wheel spin.
However, once on the slope, it felt looser in parts. And steeper than I remembered from one year prior (when I did get up there in Mud/Ruts I think).
I think over reaction with right foot almost coincided with button off.

Cheers,
Scott

PS .... worth noting the stall is a rare situation and perhaps seems like a more common scenario to the non-D3/D4 reader due to it being discussed at length in this thread.
And yes, I can get back there it's about 2 hours away so a good place for a day trip. Just for scientific research of course :)

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We are all waiting for the "test" results[bigsmile]

Watching the LRD414 video a few times. I don’t see how this is really a 'stall' in the true mechanical sense, it looks and sounds more like a software engine switch off (as mentioned by others).

I would not expect the TC to be locked at this low speed and even if it was, surely it can unlock quickly to prevent stalling the engine. I read these ZF gearboxes can select gears (lock/unlock the clutches) in a fraction of a second, so the TC locking clutch could probably release faster than stopping the engine.

My D4 is a new to me (although my forth LR) so apologies for any dumb questions. But, is there any way to use a diagnostic tool to view the status of the TC while driving? It would be interesting to know what’s happening at different speeds and terrain settings.

Also, why keep the DSC on when off-road? My understanding is the DSC helps control the vehicle in under-steer or over-steer situations at highway speeds (by applying selective braking and throttle inputs). How would this help on a steep rutted slope? There’s a lot going on with traction control anyway so having another system ‘competing’ sounds like a recipe for disaster.

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Originally Posted by NoosaMick

Any thoughts on this YouTube video?

Alloffroad #137 - 4x4 Victorian High Country Discovery 4 Rollover

I don’t fully understand how the engine would stall with an auto box and torque converter.

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I think the explanation at the end of the video sums it up and for some reason the park brake did not lock on and with what seems the left rear wheel in a hole the end result is what we see. I think as said turning off some features to go up a hill disabled the very thing that could have stopped the outcome and when it all happened the car could not respond the way it is programmed. Just my opinion.

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Originally Posted by NoosaMick

Watching the LRD414 video a few times. I don’t see how this is really a 'stall' in the true mechanical sense, it looks and sounds more like a software engine switch off (as mentioned by others).

I would not expect the TC to be locked at this low speed and even if it was, surely it can unlock quickly to prevent stalling the engine. I read these ZF gearboxes can select gears (lock/unlock the clutches) in a fraction of a second, so the TC locking clutch could probably release faster than stopping the engine.

My D4 is a new to me (although my forth LR) so apologies for any dumb questions. But, is there any way to use a diagnostic tool to view the status of the TC while driving? It would be interesting to know what’s happening at different speeds and terrain settings.

Also, why keep the DSC on when off-road? My understanding is the DSC helps control the vehicle in under-steer or over-steer situations at highway speeds (by applying selective braking and throttle inputs). How would this help on a steep rutted slope? There’s a lot going on with traction control anyway so having another system ‘competing’ sounds like a recipe for disaster.

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Good question...

Just as a diff lock can click on and out extremely quickly, it can not do it under load. Hence the instruction to back off a fraction just as you engage a diff locker (same can be done with the CDL).

In rock crawl the driveline is even more locked than normal, so there is a lot more tension in the driveline.

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Originally Posted by johntins

Indeed. The D2 was an interesting compromise, being monocoque over ladder, as were most LR cars from D2, P38A, right through to the last gen RRS. In fact, I believe the D1 gets a guernsey as well, but it wasn't nearly as safe. Just like RRCs.

Don't get me wrong, safety is good, especially for those who have kids. LR's work needs to be respected. The structural integrity of Mark's D4 saved his life. I used to tool around, on tracks like that, in a G60 Patrol ragtop. Everywhere at full throttle because that is the only way the car would get up. A crash like Mark had was easily on the cards, but the difference is, I wouldn't have survived it, unless I was thrown.

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I'm pretty sure it's the D4 that's MONO/LADDER not the D2??

I thought so too Redback although D2 was a bit of a hybrid with all the bracing and big anti intrusion beams in doors etc. Much closer to both than d1 was and a lot stronger than d1. In D1 and D2 you could remove both bodies cpmplete but D2 body had a lot of structure built in. Cheers

What a sad sad sight to see!! Glad everyone in the trip was ok and no hassles with the insurance company.

If there was a ticking sound that means the gearbox was rotating (parking pawl would have sheered immediately), which means one or many wheels were also turning.

Bit worrying as even new drivers when car moves unintentionally will stamp on the brakes, so I can’t see any difference in this circumstance. So logically either interference from electronics, or 4 locked wheels not stopping it.

I can see that stalling will occur with tc locked up, but as others have said, it should be able to unlock in milliseconds.

If loaded does that prohibit unlocking? It is a clutch plate isn’t it, so load shouldn’t be a factor. Different to an air locker that slides gears together and loading will definitely make it harder to unlock.

My TDV8 Vogue stalled last weekend. Attempting a short steep hill (wife driving). Loss of traction (traction control doing its thing) followed by snapping the throttle closed. Simple to restart in neutral.

Wow, not good. Was the D4 recovered? if so, would have been an interesting exercise.

Sorry if this has already been discussed.

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Originally Posted by 86mud

Wow, not good. Was the D4 recovered? if so, would have been an interesting exercise.

Sorry if this has already been discussed.

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Yep, was recovered and insurance paid out.
Took the best part of a day, 3 blokes and 1 truck apparently.
I didn’t get any pictures (unfortunately).