Originally Posted by Kajtek1
So following the change in topic. From what I noticed, limited slip differentials seized to exist in computer era, when it is much easier to write a program, that is using ABS system to apply brake on spinning wheel.
I've never seen strictly technical description,but generally 4WD has no central differential and can't be used on dry pavement, while AWD is for street vehicles.
Actually no. Limited slip differentials are still in use today. In fact Subaru uses a limited slip rear differential in most of its AWD 2008 line up along with ESP (electronic stability control). In fact if you buy a manual Subaru Impreza WRX STI you get no less than three limited slip differentials, a helical-type limited-slip front differential and a Torsen limited-slip rear differential and finally one for the middle to manage power between each end.
Audi use a Torsen limited slip differential in the middle of most of their cars, the left/right traction is usually controlled by electronics however but there are examples in which they have also put a limited slip in the rear.
FWD cars like the 2007 Honda Civic SI use a limited slip diff up front along with traction control and ESP.
Acura's SH-AWD is an advanced electronically controlled limited slip differential. It uses electromagnetic clutches to shift power left to right in the rear AND front to back all in one single diff unit that sits in the rear of the car.
Using computers to control clutch packs like Acura does here and Subaru does with the center diff in their automatics is about as close as you can get to eliminating the need for none electronic limited slip diffs. But its expensive and until it gets cheaper manufacturers will just use the none electronic ones especially between the axles and let the electronics handle traction control and stability instead.
The difference between 4WD and AWD is exactly as someone pointed out, you can lock 4WD into 2WD mode. AWD's do not normally have this option, however Subaru's AWD automatic transmission can be made into 2wd for emergency situations by inserting a fuse in the engine bay (its in the owners manual in the change tire section). This is not written in stone however, there is a blurring of the definitions. Like I explained with the Subaru you can have an AWD that behaves like a 4WD and you can have a 4WD that behaves like an AWD. Also manufactures like Honda will sell both types in their model line ups.
Hope this helps...
Oh and here's another little trivia, high end manufacturers still use single stage paint too
Lexus uses it on their Obsidian Black paint on their cars including the LS. So limited slip diffs and Single stage paint, both old technologies, are being used today thanks to stronger modern materials and chemicals being used to make them.