The Model 340A Engine Retarder represents the first opportunity in Jacobs's history with Caterpillar Incorporated to design the retarder during the development of an engine. This paper explains the development process improvements utilized to produce the Model 340A.There were two primary goals of the project: performance and delivery. The Caterpillar performance goal for this retarder was to bring its new engine in line with the best retarders in the trucking market without sacrificing reliability. This attention by Caterpillar engineers (external concurrent development) positively affected retarder performance and serviceability.The delivery goals were severe by past standards. This pressure resulted in incorporation of new development tools (internal concurrent development) to meet delivery as well as cost and quality goals.These efforts have resulted in a much stronger customer-supplier relationship, as well as exceeding the original project goals.