Offroad modes and terrain

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greiswig

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I feel like I'm still figuring this beast out when it comes to offroading. On Hell's Revenge and other trails in Moab, it felt like I never quite had the kind of control I wanted. For example, in rock crawling mode on the ironically-named slickrock, it did pretty well. But sometimes it felt like it governed the throttle too much: when I'd get to a ledge and needed some momentum to get me over it, it didn't want to let me do that.

I'm more used to manual transmissions with extremely low gearing, so I'm a little spoiled in this area. But I'm wondering if there is a different mode that seems to work better on that kind of trail?
 

Nechaken

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I feel like rock crawl mode softens the throttle response and severely curtails wheelspin -- possible you were trying to accelerate hard enough you got wheelspin?

Here's a copypasta from Aulro about the effects of the different modes...

GRASS/GRAVEL/SNOW Function.

Engine Management System.
More progressive throttle map to make it harder to induce wheel spin when setting off & easier to drive smoothly.
Automatic Gearbox.
Automatically sets off in 2nd gear in high range to make it harder to induce wheel slip when setting off.
Automatically selects 3rd gear in low range to make it harder to induce wheel slip when setting off.
Electronic Centre/Rear Differential.
Higher preload settings to reduce the chance of wheel slip occuring.
Hill Descent Control.
HDC is automatically switched on when in low range.
Traction Control.
Has a more responsive & aggressive tune so that if any wheel slip does occur, then it is controlled quickly.
Message Centre.
If a manual gearbox is fitted then the drive is advised to set off in 3rd gear if in low range when a different gear is selected.

MUD/RUTS Function.

Engine Management System.
More progressive throttle map to make it harder to induce wheel spin when setting off & easier to drive smoothly.
Automatic Gearbox.
Starts off in 1st gear, will remain in 1st if light throttle is applied.
Changes up with heavy throttle inputs. Stays in gear & torque convertor locks up when throttle pedal is released. Changes down gears if no throttle pedal input & speed goes below a set threshold.
Electronic Centre/Rear Differential.
Higher preload settings to reduce the chance of wheel slip occuring.
Dynamic Stability Control.
Dynamic stability thresholds are tuned to induce less engine throttle intervention.
Hill Descent Control.
HDC is automatically switched on.
Traction Control.
Traction controls tune is more responsive & aggressive & induces less throttle intervention to control excessive wheel slip quickly. But it allows higher slip levels so that traction can be generated.
Message Centre.
Recommends that low range be selected.
Recommends that the air suspension be raised to off road height.
Steering inputs are displayed when a 1/4 turn of the steering wheel is acheived.
Warns if off road height has been selected & not yet reached.
Warns if off an off road height has been inhibited due to trailer electrics being detected. (not sure if new programming has altered this).

SAND Function.

Engine Management System.
Soft intial throttle changing to more agressive as throttle becomes heavier.
Automatic Gearbox.
The gearbox changes up gears later & down gears earlier to keep vehicle in maximum torque band.
Dynamic Stability Control.
Dynamic Stability thresholds are tuned to induce less engine throttle intervention.
Traction Control.
Traction Control tune induces less throttle intervention.
Message Centre.
Steering inputs are displayed when a 1/4 turn of the steering wheel is acheived.
Warns if off road height has been selected & not yet reached.
Warns if off an off road height has been inhibited due to trailer electrics being detected. (not sure if new programming has altered this).

ROCK CRAWL Function.

Engine Management System.
More progressive throttle map to minimise wheel slip when setting off.
Automatic Gearbox.
Automatically sets off is 1st gear. Holds onto 1st gear longer & changes down to 1st gear sooner to maximise low speed control.
Transfer Box.
Rock crawl is only available in Low Range.
Electronic Centre/Rear Differential.
Has very high preload setings to reduce the chance of wheel spin occurring.
Hill Descent Control.
HDC is automatically switched on. The minimum target speed is automatically selected & the system is more aggressive so as to control the speed quickly.
Traction Control.
Traction controls tune is more responsive & aggressive so that if any wheel slip is detected it is controlled quickly.
Message Centre.
The Driver is asked to select low range.
Steering inputs are displayed when a 1/4 turn of the steering wheel is acheived.
Warns if off road height has been selected & not yet reached.
Warns if off an off road height has been inhibited due to trailer electrics being detected. (not sure if new programming has altered this).

Normal mode doesn't actually switch any of the system off or disable them, it just doesn't put them into any special mode. Hence, traction control etc is always active.

What's the difference in Terrain Response between the D3 and D4?
The D4 has Rock Pre-Crawl (applies brakes up to 5km/h in first and reverse forcing the wheels to turn against the brake).

Sand mode & Launch control: It uses a motion sensor on the chassis to detect when it is moving. Once moving, it'll then adjust the throttle response to make it more aggressive.
 

Nechaken

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I thought this was an interesting read as well. I'm sure there have been some updates since the LR3, but I assume the same concepts are being applied in our trucks too.

 

mm3846

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Interesting. I'd love to hear more about why?
From @hickersb 's descriptions, it's pretty hard to see differences.

It just feels right. I’m used to manual everything (shifters, levers, and lockers) and no traction control. And that mode works the best IMO. I haven’t had the truck in any real rocks to give the rock crawl mode a real go, yet.
 

ryanjl

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I've always used Rock Crawl at my dealership's off-road event and on the loose rocky trails in Colorado. I've never had mine on slickrock, though.
 

greiswig

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The impression that I get is that rock crawl mode is more for going up steep hills with softball-sized rocks, where wheelspin is more of a problem. Like I remember Cadillac Hill on the Rubicon being.

Slickrock is really just steep pavement for the most part, with steps and off-camber situations. I found myself wanting really firm transmission engagement, and a very predictable throttle so that I could bump myself over some of the harder obstacles. It did OK, but it was oddly slow in doing it. I ended up just using general mode for the most part, but in low range.

I'll have to try the mud mode next time I'm out there. I used that on some of our Oregon trails out in the Tillamook State Forest OHV area, and I was bloody impressed. Worked great out there.
 

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