This document seeks to classify all-wheel drive (AWD) architectures primarily based on the installed hardware and does not consider the implementation of the controls and software. For example, a power transfer unit (PTU) may be equipped with a clutch that is capable of torque management, but the control implementation only uses it for disconnection functions without torque management.
In this SAE Recommended Practice, attention will be given to passenger cars and light trucks (through Class III). The definitions presented herein may also be applicable to heavy trucks (Class 4 through 8) and off-highway applications using more than two axles but are primarily focused on passenger cars and light trucks.