Thread: Rock Crawl

Gawd! I can't answer that question but have deployed rock crawl on a couple of occasions and it's worked really well. First was to get out of sand at Bremer Bay when I got well and truly bogged.... dug out sand behind the wheels and rock crawl selected and back we went slowly.
Next time was a beauty at Carawine Gorge WA when towing our van. I was looking for a camp spot and went too far and ended up in the shale which has caught heaps of people. And there they all were with big grins on their faces, the big hat and beard mob who drive mine site type vehicles. Put her in extended mode and selected rock crawl and crawl she did, right out in front of their noses.
This was not only pleasing to us but another Disco owner who couldn't contain his delight with much waving and thumbs up for us.
Funny how the other lot all turned their backs on us.
AlanH.

I believe it is not fully locked in the true sense (like on older models where the centre diff is either fully locked or fully open) but rather in Rock Crawl it applies a high torque preloading to the clutch pack to minimise any slip.

Can still get transmission wind up in the drive train, but if excessive it will cause the clutch pack to slip.

Extended improper use can accelerate wear of the clutch pack, but if it overheats then it defaults back to an open diff until it cools down.

I always think RC is for walking speed difficult sections or as a get out of jail function.

This is from the Sticky Section;


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.

Originally Posted by PerthDisco

I always think RC is for walking speed difficult sections or as a get out of jail function.

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.

Thanks - that is very informative but does not actually say whether the CDL is locked or not or is variable like the other TR settings.

Cheers

Garry

Originally Posted by 101RRS

Thanks - that is very informative but does not actually say whether the CDL is locked or not or is variable like the other TR settings.

Cheers

Garry

I read it as saying it (like everything else) is ultimately variable but set to react quickly and lock up aggressively at the first sign of trouble expecting that any slippage is not wanted.

The amount that the CDL locks is variable. If you had the display you’d see it lock, partially lock and unlock according to the terrain

The centre diff will allow slip by varying degrees if the steering is turned more than just a little and depending on how sharply the steering is turned. If a front CV joint is busted then turn in very wide arcs to avoid unlocking the centre diff although the centre diff will unlock after a while anyway to relieve pressure on the clutch mechanism for longevity as the mechanism isn't as robust as that in the rear e-diff. When using rock-crawl to drive out of bogs be sure to keep the steering as straight ahead as possible, at least initially to get moving.

I don't think it completely unlocks... In our MY16 I have noticed that immediately once "Rock Crawl" is selected, the centre diff icon turns orange. When moving it turns red and stays so untill you go over a certain speed or turn past a set steering angle where it goes back to orange. In most other modes, usually the symbol stays green and changes colour as the terrain requires it to change. Even normal mode operates this way..

Il take some pictures next time I am out.