This paper conducts threat analysis and risk assessment for an integrated Automated Manual Transmission (AMT). Based on the identification of eight core security assets, including Controller Area Network (CAN) messages, firmware, etc. potential damage scenarios are analyzed, and the impact rating is quantified from four dimensions: safety, property, operability, and privacy. For each damage scenario, possible attack path are reversely analyzed to construct threat scenarios, and the attack feasibility is comprehensively evaluated from five dimensions: time, expertise, product knowledge, window of opportunity, and equipment. Finally, by combining hazard levels and attack feasibility, the risk matrix is adopted to determine the risk level of each threat scenario, and corresponding treatment strategies such as reduction, transfer, or retention are proposed.