> The downside is you shouldn't use it over 10mph or so.

That's not strictly true, and varies between implementations/transfer case designs. In Jeep Wranglers, for example, which have both high and low gearing options in 4WD, the owner's manual will indicate that you can drive at any speed (on loose surfaces such as sand or dirt) in 4HI and 0–25 MPH in 4LO.

You right that's why I said 10 or so. Try taking a turn at 25 in 4LO. I'm not sure of the use case for 25 in LO. My Grand Cherokee can operate the same way but I doubt I would go into LO at those speeds. It also will switch to 4HI when it detects wheel slip.

A friend of mine had a old truck that would randomly switch to 4LO on the highway. It's pretty scary driving 60 and having 4LO switch on.

In dirt taking the turn at 25 is fine. The inside wheel will just spin a little.

Outside wheel wants to travel more than the drivetrain so it would slip, not spin correct?

The inside wheel would spin if the outside doesn't slip.

More often than not, even more so than slip, the outer wheel will "hop". This is especially true, if you've done something potentially unintelligent like welding the spider gears together.

Not sure why you're getting downvoted. On high traction surfaces like dry pavement, the outer wheel does tend to hop during turns.

Oops you are correct

Any new Land Rover or Range Rover? They come with 2 locking differentials, with 3rd being an option that can be added extra. Same with Mercedes G-class - they come with 3 locks as standard. And I've no idea what you mean by "cars don't have proper ground clearance" - just buy a one that does?

I don't think you understand what I mean. When I say car it doesn't include SUVs/trucks. The difference used to be cars (unibody) vs SUVs/trucks (body on frame). A lot of SUVs are now unibody including my Grand Cherokee.

There are many types of SUVs and trucks with 4wd in the US. I guess in Europe you only have Land Rovers or G-wagons. I don't think GLs or MLs are common in EU but you can get beefed up off road packages in the US.

As I explained in my other comment - I forgot that in US, "car" and "suv" are two different things. You could have a Ford F150 or a Chevy Escalade here and it would still be a "car" , just like a car without roof is still a car but of a subtype "cabriolet".

>Any new Land Rover or Range Rover? They come with 2 locking differentials, with 3rd being an option that can be added extra.

Source? Center locking diffs are more or less standard, rear lockers are options in LR3/4/post 2004 Disco's, Sports and Range Rovers (although standard in some, I think the Supercharged and possibly the SVRs, but I'd need to check) Front lockers are not factory options and I don't ever recall seeing after market lockers for these models advertised.

Defenders, Discos upto 2004, Range Rover classics (and probably P38s) and all series vehicles have the standard after market options for front and rear lockers.

I had a 2005 Discovery LR3 V8(US Spec, imported to EU) and I could swear it had 3 diffs - at least the 4x4 Info screen would always show 3 diffs working independently when I was driving it offroad. Of course I might be remembering it incorrectly, but a quick search on google shows "genuine Land Rover Discovey 3 front differential" part on ebay, so I guess it must exist?

http://www.ebay.co.uk/itm/like/182246825443?lpid=122&chn=ps&...

They have differentials on the front, but they're not "locking" differentials, they're "open" differentials, no locking capability at all.

Center diffs are for the most part (in Land Rovers) locking differentials, though some Discovery IIs had open center diffs and things like Freelanders use a viscous coupling in place of a mechanical diff lock.

Newer models have an electronically controlled locking diff in the gearbox (center) and an optional electronically controlled locking differential at the rear.

But front diffs on modern Land Rovers are open.

Edit: Here is an image showing the locking diffs on an LR3/Discovery 3: http://www.landroversonly.com/forums/attachments/f41/37257d1...

Note the center diff is unlocked (or open) and the rear is locked, there is no option to lock the front, which will always be open.

I think he means regular 'cars' rather than 4×4s (or SUVs).

Sorry, I forgot that in US "cars" and "SUVs" are two different things. Where I am from there is no such distinction, a Land Rover is still a "car".

Yes, here too. It's especially confusing now as the line between the two is increasingly blurred.