Engines developed to meet the requirements of the North American heavy duty truck market must meet the EPA/CARB on-highway emission regulations as well as the reliability, cost, performance, and sociability required by the customer. Developing engines to meet these requirements takes not only unique design approaches, but also must fulfill process and application requirements. This paper summarizes development of the Caterpillar 3406E heavy-duty diesel engine using several unique approaches.The 3406E, a six cylinder, 14.6 liter, in-line, heavy duty diesel engine is the newest generation of the proven 3406C Engine. Concurrent product and process development methods were utilized for the 3406E, starting with defining customer requirements through Quality Functional Deployment (QFD). Failure Mode and Effect Analysis (FMEA) was also applied throughout the development.The 3406E Engine uses the basic design and manufacturing/assembly processes of the 3406C Engine and adds electronic unit injectors with enhanced electronic controls to meet future regulatory and customer requirements. The 3406E Engine has substantially fewer components than the 3406C Engine. The major design changes include a new cylinder head with integral air inlet manifold and overhead camshaft, unique front gear train, and new electronic control module.