Thread: D4 Rollover

Originally Posted by ozscott

So do we know why they stall under these conditions? It's not the first i have see. Do that. Cheers

Cause its locked up,just like a manual,if the wheels had kept spinning,it wouldn't have stopped,i presume.

Difficult to tell throttle position when it came down,but it sounds like the driver backed it off,which means it has more chance of stalling.

Pity Gordon isn't here to answer your question with a better explanation,he is an expert on this type of stuff.

Yep I wondered if locked but assumed that torque converter would have had sufficient slip. Cheers

Cheers

Originally Posted by scarry

Cause its locked up,just like a manual,if the wheels had kept spinning,it wouldn't have stopped,i presume.

Difficult to tell throttle position when it came down,but it sounds like the driver backed it off,which means it has more chance of stalling.

Pity Gordon isn't here to answer your question with a better explanation,he is an expert on this type of stuff.

I did ask Gordon for his opinion. This is what he said (below). Hope he does not mind me posting it up here (too late now I suppose). He only looked at the video and none of the discussion subsequent including Marks version of events. I also asked specific questions to which he was responding. I have a rotary dial selector unlike Marks earlier model.

"Most of the explanation in the video makes sense, but the stall shouldn't have happened in the first place. When the front wheel hit the rut and wouldn't pull the car out, I'd suspect that the driver panicked a bit and either flattened the accelerator into the floor, or backed off the pedal completely, both of which could produce a stall. In Rock Crawl, it's always gentle changes on the accelerator, otherwise the DSC will cut in and kill the power.

IF you stall a D4, flick the rotary into neutral and restart. If you're sliding backwards with all 4 wheels locked (which would be the case if he was on the brake pedal), then immediately engage drive and release the brake whilst gently accelerating.

Yes absolutely you should always have the hill decent on, and the DSC as well, when climbing steep, slow ascents."

It is good that there is some discussion around this.
I’m not claiming to be an expert, but at the same time I’m not a complete novice. For me a few things have stood out so far

1) get the line right !!! I was about 10 cms off by my reckoning.
2) HDC...use it on steep inclines also. It sits in the background and hopefully would’ve controlled my rollback better.(with engine on or off apparently)
3) the vehicle can stall on hills...park brake immediately. There has been some discussion already about the auto park brake (on the 8 speed gear box). My vehicle did not have this, putting the car into park started the roll back and a clicking could be heard as the gear mechanism had not locked fully.

I am still confused why I rolled back down the track in the first place. Brake boosting would’ve been lost due to the stall, but brake pressure was available and I was planted on the brakes. It did roll back, for whatever reason...HDC / park brake should’ve stopped this.

Hopefully, at least 1 other person learns something from this...and leave Mike (rocmic) and myself in the rollover club!

Cheers

Originally Posted by Tombie

That stalled because it was in TC lock up and came to an abrupt halt...

Originally Posted by scarry

One thing i do know is mine has stalled,and it was on a steep rocky hill in rock crawl.

I've stalled I think 3 or 4 times, always in Rock Crawl and always with an abrupt halt or backing-off throttle.
I suspect I have backed off too quickly and/or too much right foot. Two of them have been caught on video.



First one; the rocky slope was very steep and previously had much less exposed rock step.
Tyre pressure too high and perhaps too aggressive. The delay in restart is waiting for the rotary dial to go into Park, which it did automatically.
The second one; it did bog down in sandy gravel thanks to relatively high tyre pressure and big holes already churned up. Probably should have been in Mud/Ruts.

Scott

Originally Posted by SimmAus

There has been some discussion already about the auto park brake (on the 8 speed gear box).

This is not a standard feature for the 8-speed. It does however automatically move to Park once stalled.

Tombie, when you say "TC" do you meant traction control or transfer case?

Originally Posted by Eevo

Tombie, when you say "TC" do you meant traction control or transfer case?

Torque Converter maybe