The Power Transfer Unit (PTU) provides full time, part-time or on-demand All-Wheel-Drive (AWD) torque distribution for Front-Wheel-Drive (FWD) based AWD systems. FWD has advantage in drivetrain efficiency and fuel economy and AWD improves traction to have better acceleration and handling. Part-time and on-demand AWD have all the benefits of AWD and the efficiency of FWD so continue to be popular around the world. However, Noise, vibration and Harshness (NVH) error state called PTU rattle has been detected in FWD mode of AWD systems due to torsional excitation. This study develops an AMESim-ADAMS co-simulation model for PTU rattle assessment through PTU case vibration. The correlated one-Dimensional (1-D) torsional model simulate the operation condition of PTU rattle provides the torsional input to excite ADAMS three-Dimensional (3-D) PTU model to recover PTU case vibration. Hence, PTU rattle can be assessed in Computer-aided Engineering (CAE) analysis by applying the target defined from test data with respect to PTU case vibration. The critical measurements for correlation are also investigated and treated as indicators. This co-simulation model will be capable of evaluating PTU rattle risk and developing countermeasures. Future work is to study the PTU case boundary condition to improve the non-rattle region case vibration level.