A method for making catalytic converters with automated crack detection includes forming a rigid housing, providing a substrate shaped for reception in the housing, and forming a mat shaped to cover the exterior surface of the substrate and having a thickness which creates a tight friction fit between the substrate and the housing when the same are assembled. The mat is wrapped around the substrate, and the wrapped substrate is then stuffed into the housing using a reciprocating ram or the like that extends at a relatively constant speed. The stuffing force and the ram position are measured and recorded regularly to define an array of data. The data is analyzed for any abrupt changes in the stuffing force as a function of the ram position indicating a crack in the assembled substrate.