This project aims to investigate how vibrations are transmitted between different shafts in a jet engine, known as cross-shaft coupling. Most modern jet engines have split compressors each driven by its own turbine, with the speed of rotation increasing at each stage for improved aerodynamic efficiency. This allows for a more compact design for the same thrust. However, current modelling techniques do not accurately predict the transmission of vibrations from one rotor to another, due to the complex interaction of shafts, rolling-element bearings (REB) and squeeze film dampers (SFD). Previous work has concentrated on developing models of the individual components and this has not been straight forward, so incorporating them into a system level model is expected be extremely challenging, because there could be sub-harmonic, instabilities or even chaotic motion. Validation of the model will be performed against a test rig which will be developed in a parallel activity. The ultimate aim is to deliver fully validated lightweight models of the relevant components, and to provide insight into the mechanisms involved in these phenomena .