Difference between AWD and 4WD?
Part-time 4WD is the original 4WD system and the most basic.
As with Full time 4WD there are several options available to the
driver. In normal conditions the vehicle is driven in two-wheel
drive, usually powering only the rear wheels. 4WD mode can be
selected either by a separate mechanical lever or by an electronic
switching system
AWD systems also lack the 'low range' feature which is common in
most 4WDs.
The AWD system is less effective and more fragile than the 4WD
system in a situation where high torque is required. Indeed, the
viscous coupling units simply cannot satisfy high torque demands
when the vehicle is offroad. AWD vehicles tend to be more 'car'
like than obvious offroaders.