Sorry J1
When it has a full chassis that extends the entire length/width of the vehicle, that can have a variety of bodies and accessories bolted on to it, mostly separately articulated; and it's primary purpose is the carriage of goods.
When I replied to this last night while mostly brain dead, I mentally substituted the words "4WD" for "SUV" and "truck" for "4WD" ... DOH!
Of course what many have said here is correct. There are many "SUV" (I also prefer the term "soft-roader") vehicles that are 2WD, or only have 4WD/AWD on demand. This is usually about 1/2 second too late, as someone has already mentioned.
Constant AWD vehicles are a whole other kettle of fish - e.g. Audi Quattro diesels, Subaru Foresters (in particular), and a whole swag of vehicles that run free-wheeling front hubs to improve fuel consumption from downright lousy to barely acceptable - had those on my '68 LC ...
. With my FWH, I had to stop, get out, manually engage them, then proceed. That didn't make my (light) truck, any less of a 4WD,
or any less of a primitive light truck ...
My Forester (2006) has a theoretical torque split of 50:50 F:R. It probably only does this very occasionally, and then probably only on the way through, on a straight bitumen road ...
. It is normally constantly variable between 60:40 and 40:60, but will vary this too if subjected to extreme conditions. It has a viscous LSD in the centre, and a vLSD in the rear.
My Forester has a 5MT box with full synchro HR/LR. The Subaru OM tells me not to exceed 188 kmh in 5th/LR ...
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The car has a theoretical top speed of about 213 kmh (5600 rpm at maximum power, translated into kmh in 5th/HR), but is speed limited by the ECU to 198 kmh.
Some members over at the ORS forum have modified Foresters with a 3.0L H6 engine fitted and engineered,
DCCD centre diff, plated rear diff and
Torsen helical diff in the front (the front diff is part of the gearbox in Subies). The standard setup works brilliantly for me, but I'm not into doing the ultimate off-road thing. Did all that when I was a lot younger, and have no need or desire to re-live my misspent youth ... ROTFL!
More or less back on topic, a friend has a Suzuki Grand Vitara. While it is very similar on the surface to my Forester, that's where the similarity ends. The Zook is basically a Mack truck that's been washed and left out in the sun to shrink, while mine is basically a high speed rally car that's been tricked up to look like a (relatively) small off-roader (I can't bring myself to think of a car that weighs nearly 1.5 tonnes as "small"!). The Zook has all sorts of truck type features under it's skin, mine hasn't. However I drive my car whenever me and my mate go out photographing together, and he reckons that other than robustness, the Forester beats the crap out of his Zook for everything else, and at least equals it for off-road stuff. He prefers not to drive, these days, and is prepared not to sh!t himself when subjected to my sometimes quite 'spirited' driving ...
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Get into my SWMBO's 2009 SH Forester and the game changes again. It has the same engine as mine (EJ-253), but uses the Subaru 4EAT transmission. This came in two flavours - standard 4EAT and "Sportshift" 4EAT. The Sportshift uses the ProDrive technology for the TCU under licence and a different kind of clutch pack in the centre diff. It does not use a vLSD in the centre diff. It also has both the rear vLSD and EBD plus VDC. With the ProDrive TCU, one can drive it like a manual without wrecking the transmission ... She doesn't, of course! The VDC can and should be switched off when on dirt or off-road, and Subaru recommends this. It doesn't change lots of what it does, but it does tell the vehicle to forget about stability and concentrate on traction. Apparently this works very well in dirt and off-road situations - something my wife is yet to do, and probably never will ...
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People should also bear in mind that some highly capable 4WD/AWD have auto boxes, so have no need of a LR gear set ...