Development of a Clunk Simulation Model for a Rear Wheel Drive Vehicle With Automatic Transmission

A reduced model is developed for transient analysis of gear rattle in an automatic transmission (AT) powertrain. Linear modal analysis for the reduced order model compares well with a detailed model that includes planetary gear dynamics. Clearance type lash functions are used for the reduced geared coordinates of the automatic transmission and final drive. Impacts within the gear pairs are affected by the engine surging, shaft stiffness, component inertias, engine harmonics, drag torques, braking, viscous damping and vehicle load. The occurrence of these impacts, or clunk, from shuffle and axle oscillations is demonstrated under typical driving conditions.