When to use 'low range'

[yabadaba]

Guys, I've been driving as sensibly as I know how over the last few days and haven't got into any difficulties at all in my 2005 Jeep Grand Cherokee....with one exception...attempting to come to a stop with only ice under the tyres.

I've tried to keep the actual braking to a minimum and have let engine compression do most of the work (when the auto drops into first), but things have still got a little hairy at times! Now, although I've been driving for nearly 20 years, I'm new to AWD vehicles so please forgive what might sound like a dumb question, but can all you 4x4 experts out there please let me know if this is when I'd be better off engaging 'low gear'?

[Sixpackpert]

In my experience Low Ratio is only needed when doing off roading down steep inclines or recovering someone else who is stuck!

As you can't (in my vehicle anyway, yours may be different) switch from Low to High ratio when on the move it is pretty pointless on the road as you would have to stop to switch to the high ratio box.

You could, I suppose, stop at the top of a hill, engage low ratio to go down the hill in a controlled manor and then stop at the bottom to go back into high ratio but I would think you would then become a hazard for all other road users who can't go that slow and end up with someone in your boot!

[yabadaba]

Sixpackpert said:

You could, I suppose, stop at the top of a hill, engage low ratio to go down the hill in a controlled manor and then stop at the bottom to go back into high ratio but I would think you would then become a hazard for all other road users who can't go that slow and end up with someone in your boot!

Yes, I was thinking that too....might end up doing more harm than good! I can actually switch into low ratio on the move, but have to be moving very slowly, like 3-4mph max and the gearbox has to be in neutral to do the shift. Maybe best avoided then.

[GKP]

Not avoided, but used with caution simply for mechanical sympathy. If you've just reached the top of a hill and know that there's a long descent to a junction, it may well be advantagious to plop it into low and use 2nd or 3rd gear to trundle down in a controlled fashion.

[gdaybruce]

If you want to keep the speed right down to a crawl it might be worthile going for low ratio but be aware that in sheet ice conditions you can have too much engine braking, such that the wheels lose traction and you find yourself sliding downhill with the engine just ticking over and the wheels turning at tickover speed. I've had that happen in both rear and front wheel drive cars when decending in 1st gear and it's not a pleasant experience! Obviously less likely with 4wd but ice is ice, however many wheels are sharing the traction. Basically, in those conditions your best bet (if you're already committed to the hill) is to keep the wheels turning so that you have some steering and hope you can either get to the verge or kerb where there might be more grip or can reach the bottom without hitting anything too important!

[JM]

As said by others, low range is normally reserved for more tricky situations off-road, when going really slowly is necissary or a lower gear or two is required.

I have used it on steep hairpin bends in the snow and ice and it got my round and down safely, the slowest tick-over in 1st (auto) was still too fast, so low range and locked in to 1-2 on the box and just on tick-over crawled along, no drama.

Could also be usefull for getting through a drift or two and would be great for pulkling out someone who is stuck.

[chris116]

gdaybruce said:

If you want to keep the speed right down to a crawl it might be worthile going for low ratio but be aware that in sheet ice conditions you can have too much engine braking, such that the wheels lose traction and you find yourself sliding downhill with the engine just ticking over and the wheels turning at tickover speed. I've had that happen in both rear and front wheel drive cars when decending in 1st gear and it's not a pleasant experience! Obviously less likely with 4wd but ice is ice, however many wheels are sharing the traction. Basically, in those conditions your best bet (if you're already committed to the hill) is to keep the wheels turning so that you have some steering and hope you can either get to the verge or kerb where there might be more grip or can reach the bottom without hitting anything too important!

I found this out the hard way a couple of years ago when I tried to go down the hill outside my house in a 320d. I was in first gear only doing maybe 5-10mph when suddenly I was looking down the road out of the side window! I ended up sliding about 20 yards down the road at 90 degrees, luckily at that point there were no cars parked on the side of the road as my road is quite narrow and I came to a halt with my rear bumper about 6 inches from one of the keep off the grass signs on the verge. It scared the crap out of me at the time.