Diff locks.

bigleonski · Nov 2, 2023

Tazzieman said:
Yeah mate but can she do Gunshot Creek eh

I say it could, but it won’t be mine, I’ve already driven past it once, have no problem doing it again

Tazzieman · Nov 2, 2023

bigleonski said:
I say it could, but it won’t be mine, I’ve already driven past it once, have no problem doing it again

The long drop though?

bigleonski · Nov 2, 2023

Tazzieman said:
The long drop though?

Sorry that’s what I meant. That drop is only for 20 year olds in old patrols and hiluxes.

And yes the IG could do it, like most decent 4wd’s could. Biggest obstacle with that is approach angle and getting stuck at the bottle nose first in the mud. At least the IG has a good one.
Not saying there won’t be damage though.

Tazzieman · Nov 2, 2023

bigleonski said:
Sorry that’s what I meant. That drop is only for 20 year olds in old patrols and hiluxes.

Luckily they're all restricted to social media!

bemax · Nov 2, 2023

Jean Mercier said:
On my Grenadier event last weekend, the Dutch instructor, a "real" 4x4 expert, told us the Hill Descent Control was just faster and more accurate than any human being could be!
I repeat, the guy is a real expert!

The HDC does brake the wheels individually in regard to the torque they can deliver. A human driver is not able to do so as we only have one pedal to brake. Engine brake can not do this in such a sophisticated way neither. To be fair, the incline has to be very steep and slippery to get the full advantage. Most drivers probably will never try to make such an approach as it might well won't work out well.

Lollo050968 · Nov 2, 2023

stickshifter said:
Low range in the Grenadier is 2.5:1 - and in the gas Grenadier, the engine, with this low range ratio, does not provide great braking while going down steep hills off-road. I'm sure you are right that the diesel does a better job holding down the speed.

Ineos likes to point out that the 2.5:1 ratio lets you go pretty fast in low-range, but I don't need to go fast in low range. I need low range to keep me moving slow while descending steep rocky terrain. With an 8-speed transmission, the best low range ratio for my use is 4.0:1. With this low of a low-range, I can still go plenty fast in 8th gear in low range, but I can also crawl super-slow down a steep slope without touching the brakes, and without using HDC.

I drive the Petrol Version, and I can tell you with HDC and without HDC, but Low Gear, middle Diff blocked, in manuell gear1, the Grenny is so slow, that you want to go in gear 2…. In direct comparism to the Diesel Version on same track, was no difference ….
Experience 2 weeks ago in Mammut Offraod Park together with 11 different Grenadiers.

Spjnr · Nov 2, 2023

stickshifter said:
Low range in the Grenadier is 2.5:1 - and in the gas Grenadier, the engine, with this low range ratio, does not provide great braking while going down steep hills off-road. I'm sure you are right that the diesel does a better job holding down the speed.

Ineos likes to point out that the 2.5:1 ratio lets you go pretty fast in low-range, but I don't need to go fast in low range. I need low range to keep me moving slow while descending steep rocky terrain. With an 8-speed transmission, the best low range ratio for my use is 4.0:1. With this low of a low-range, I can still go plenty fast in 8th gear in low range, but I can also crawl super-slow down a steep slope without touching the brakes, and without using HDC.

In practical terms, it's all down to the use case of the vehicle. The Grenadier wasn't designed as a rock crawler (although it won't be bad at it), unlike the jeep wrangler rubicon with its 4.1 ratio.

However when I was in Albania, my low range gearing was more suited to the mountain switchbacks of the Theth route than the JL rubicon that accompanied me. The 1st in the Grenadier is very low, so I was between 2nd and 3rd low range most of the time, but it wasn't too low and Jerky. The Jeep was in the awkward area between ranges range, not having the legs to stay in L on the straight gravel sections where speeds increased.

I think 2.5 to 1 is a more all-round low range ratio suited to the Grenadiers all purpose use case. It's better in sand for instance, but still plenty low enough to push a 3.5ton trailer uphill in reverse with the brakes on... don't ask me how I know this..

The wranglers aren't designed with all the utility duties of the Gren in mind, so can dedicate themselves to one thing, which is crawling rocks like nothing else can imagine

hopefulkiwi · Nov 2, 2023

Spjnr said:
In practical terms, it's all down to the use case of the vehicle. The Grenadier wasn't designed as a rock crawler (although it won't be bad at it), unlike the jeep wrangler rubicon with its 4.1 ratio.

However when I was in Albania, my low range gearing was more suited to the mountain switchbacks of the Theth route than the JL rubicon that accompanied me. The 1st in the Grenadier is very low, so I was between 2nd and 3rd low range most of the time, but it wasn't too low and Jerky. The Jeep was in the awkward area between ranges range, not having the legs to stay in L on the straight gravel sections where speeds increased.

I think 2.5 to 1 is a more all-round low range ratio suited to the Grenadiers all purpose use case. It's better in sand for instance, but still plenty low enough to push a 3.5ton trailer uphill in reverse with the brakes on... don't ask me how I know this..

The wranglers aren't designed with all the utility duties of the Gren in mind, so can dedicate themselves to one thing, which is crawling rocks like nothing else can imagine

the grenadier has a very good crawl ratio (ie the gearing of low low is 56 to 1 the petrol i think is fractionally better

Michael H. · Nov 2, 2023

hopefulkiwi said:
the grenadier has a very good crawl ratio (ie the gearing of low low is 56 to 1 the petrol i think is fractionally better

Diesel is 56:1 (or more precisely 56.4:1)
Petrol is not quite as good at 53.8:1

Tinerfeño · Nov 2, 2023

The low-low figure is very important and that's great on IG. And if the autobox can hold torque converter locked on engine braking HDC will be practically useless, and certainly if there are diff locks on axles.

My Disco 1 has something like 45 and with Ashcroft underdrive engaged 120.

I'm not too much for the eletronic stuff. It's good to be there because it's cheap and may be useful to some people/conditions. And if anyone is interested we may start a new topic on eletronic off-road assist systems. I may have something concering New Defender ...

bemax · Nov 2, 2023

Michael H. said:
Diesel is 56:1 (or more precisely 56.4:1)
Petrol is not quite as good at 53.8:1

but the crawl speed is nearly the same due to the lower idle speed of the diesel.
I did not find the source for this, but it should be correct. Maybe someone here recalls where the actual crawl speed has been published. Probably in one of the off-road magazines.

Michael H. · Nov 2, 2023

bemax said:
but the crawl speed is nearly the same due to the lower idle speed of the diesel.
I did not find the source for this, but it should be correct. Maybe someone here recalls where the actual crawl speed has been published. Probably in one of the off-road magazines.

I think you mean the lower engine idle of the petrol.

Both the diesel and the petrol have a crawl speed of 2km/h.

bemax · Nov 2, 2023

Michael H. said:
I think you mean the lower engine idle of the petrol.

Both the diesel and the petrol have a crawl speed of 2km/h.

but isn't the diesels idle lower than the petrols?

Michael H. · Nov 2, 2023

bemax said:
but isn't the diesels idle lower than the petrols?

Diesel is 800 rpm
Petrol is 750 rpm

So as you suspected, the lower idle speed of the petrol cancels out the diesel's slightly better crawl ratio, giving them both the same crawl speed.

stickshifter · Nov 2, 2023

There is no "best" crawl ratio. As Spjnr said, its all dependent on what the vehicle is being used for.

The Sport version of Jeeps have a low range ratio similar to that of the Grenadier (2.72:1 in the Jeep and 2.5:1 in the Grenadier). The axle ratio in the Jeep Sport is 3.73:1, while in the Grenadier it is 4.10:1. As a result, the crawl ratio in each vehicle is similar.

The Rubicon version of Jeeps are designed as rock crawlers, with a 4:1 low range, an axle ratio of 4.10:1, front and rear lockers, and a disconnecting front sway bar. In this version, the manual transmission has a crawl ratio of 100:1, while the auto version is 77:1. If you are primarily rock crawling, this is much better than the (gas/petrol) Grenadier crawl ratio of 54:1. With a super-low crawl ratio, the engine-braking in the Rubicon is superb, and provides excellent control on steep technical descents. It is only on the steepest terrain (or when there is fine sand on top of Moab slick-rock) that tires will actually slide. I took a couple of laps on the off-road course in Colorado Springs in a Grenadier; unfortunately, first gear in low-range was not able to prevent the vehicle from accelerating down the steepest descents.

If you are not primarily rock crawling, and you mostly use low range for other types of off-roading (sand, moderate trails, etc.), then a crawl ratio of between 50:1 and 60:1 is more useful.

255/85 · Nov 2, 2023

Tinerfeño said:
That's for non-experienced and for automatic transmissions

Hi-Low with manual transmission it is very simple with double clutching. Autobox is difficult and I don't recommend trying. Automatic does it more easily at slow speed than standstill.

Center diff lock doesn't care about speed, just wheel spin. I have engaged it on Land Rovers at 80 km/h.

I doubt you can double clutch a chain drive transfer case into low range as the low range gear sets are generally planetaries. That's a lot of metal to get moving and would like require upshifting the transmission to a higher gear first to drop the revs at the transmission output shaft before going double, triple, or even quadruple the rpms the planetaries will need to increase by. If you can do it I am duly impressed

. Anyway, I think I'd hate to see your low gears at rebuild time if I'm honest.

The problem remains with the Grenadier, though. It's fitted with an auto trans (which may be plenty smart to make rev matching possible if somehow programmed to do so) and there's no neutral position inside the 'case. The range fork only mates the shift hub directly into the dog teeth* of the low-range gear.

May have to drive more in center unlocked low range as you suggest. We just hate being out in the roadway and having to slow too much for the other drivers to tolerate. Americans are nothing if not impatient on the highway.

*That might not be the right nomenclature.

255/85 · Nov 2, 2023

stickshifter said:
Low range in the Grenadier is 2.5:1 - and in the gas Grenadier, the engine, with this low range ratio, does not provide great braking while going down steep hills off-road. I'm sure you are right that the diesel does a better job holding down the speed.

Ineos likes to point out that the 2.5:1 ratio lets you go pretty fast in low-range, but I don't need to go fast in low range. I need low range to keep me moving slow while descending steep rocky terrain. With an 8-speed transmission, the best low range ratio for my use is 4.0:1. With this low of a low-range, I can still go plenty fast in 8th gear in low range, but I can also crawl super-slow down a steep slope without touching the brakes, and without using HDC.

Auto transmissions have changed dramatically since them olden days when they provided little compression braking. With modern lock-up torque converters you'd think they'd have solved the issue by now but I have no idea. I drive THM350s and THM400s so I'm truly ig'nant.

Diesels traditionally don't have good compression braking despite higher engine compression ratios due to the lack of a throttle valve creating engine vacuum. There's some useful restriction in the intake system at idle and without boost but diesels will keep breathing nearly ad infinitum in my experience. Gas engines tend to have a lower idle speed as well so that is a further restriction and a plus for petrol engines in my book. For downhill I think there's nothing like a manual trans mated to a petrol/benzine/gasoline engine and granny low. That's just my opinion, of course, but there's some experience behind it. Crawling up? That's another story.

I have seen several videos of Grenadiers using HDC and still locking up wheels on slippery descents. I think most of these were early PTO vehicles or earlier test drive vehicles (think the three guys from South Africa who opted for low-range and first gear vs. HDC - around that time). Steep hill descents can be broken up into several types like slippery/poor traction, rocky/bumpy with good traction, etc. There's probably no one-size-fits-all approach.

4.0:1 would have been nice for some but a 3 speed transfer case would've filled the bill for everyone concerned - Hi, Lo, and Damn That's Slow!

Clark Kent · Nov 3, 2023

255/85 said:
Auto transmissions have changed dramatically since them olden days when they provided little compression braking. With modern lock-up torque converters you'd think they'd have solved the issue by now but I have no idea. I drive THM350s and THM400s so I'm truly ig'nant.

Still early days for me in discovering the tuning on the ZF 8HP76 in my diesel M1 but it does seem quite smart. I was pleasantly surprised when I first hooked up my offroad hybrid camper and coasted downhill out of my street. The auto sensed the overrun because I was being pushed by the weight of the camper. It downshifted then held a low gear to increase driveline braking. An older auto would have upshifted in the same closed-throttle coasting conditions.

Tazzieman · Nov 3, 2023

Clark Kent said:
Still early days for me in discovering the tuning on the ZF 8HP76 in my diesel M1 but it does seem quite smart. I was pleasantly surprised when I first hooked up my offroad hybrid camper and coasted downhill out of my street. The auto sensed the overrun because I was being pushed by the weight of the camper. It downshifted then held a low gear to increase driveline braking. An older auto would have upshifted in the same closed-throttle coasting conditions.

Mine drops to 3rd or 4th down the steep hill from my house towards a hwy.
Same as our auto trans cars did 15 years ago!
Retro feature

hopefulkiwi · Nov 3, 2023

all i know i that my 2.8 6 sp auto diesel is a very good descender. There is absolutely no running away in 1st gear. It will increase speed in 2 and third of course. I have absolutely no doubt that outside rock crawling /rock steps sorta stuff 56 to 1 will suit me just fine

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