a bit of 4x4 knowledge here
2 wheel drive, is a system where only one set of wheels, either front or rear, gets power, it has a diff there that splits the power so you can turn smoothly
full time 4x4, or all wheel drive has power to 2 sets of wheels with a diff in each axle. it also has a center diff in the tcase, that way power can be delivered to all wheels but it will suffer no driveline bind as only the wheel with the least amount of resetence will be driven.
4x4 has either no center diff, or a locked center diff so each axle has a wheel with the least resistance being powered. You can get driveline bind and break stuff on low shear surfaces such as a road with this so in order to make FULL TIME 4x4 they include the center diff.
Full time 4x4 is best as a road system, part time 4x4 is best off road, a full time 4x4 with a center locker does as well as a part time 4x4 when it is in 4x4 offroad. Most all wheel drives do not have a low range, most part time 4x4s do, so a part time 4x4 is desirable as an offroad vehicle as it can go places the full time will not.
Another thought, a diff, splits the torque between each wheel 50/50 always, however the wheel with the last resistence is the one that tells how much torque is required, if one tire is on a road requiring 50 pounds of torque to turn, and 1 is in the mud requiring 10 pounds, then only 20 pounds will be developed and the mud tire will spin and the pavement tire will stay still, to overcome this we have
Limited slip diffs, and diffs with lockers, the diff with a locker makes sure both tires turn at the same time, so the torque will have to be 100 pounds and it will walk out of the above situation with ease, the diff with a
Limited slip will transfer either through a clutch pack or a gear pack the resistance from the stuck wheel to the turning wheel until 100 pounds of resistance is developed and it walks out. This could take a second or two and is kinda like turbo lag, not only that but depending on how well cared for the diff is, it may not do it at all.
Hope this helps about the
QuadraTrac question