Lack of good sealing of the interfaces between the various components of the automotive powertrain can affect its functionality, performance and efficiency. The performance characteristics of a gasketted or sealed joint (or assembly) in the powertrain, are its sealability, the strength of the flanges under assembly loads and the long term bolt torque retention under material degradation due to creep. A CAE approach has been presented to design, evaluate and optimize automotive powertrain gaskets, seals and gasket/seal assemblies under assembly conditions. In this approach, the shape of the gasket/seal cross-section is optimized to maximize sealing pressure, and the gasket/seal assembly is optimized for its performance characteristics. The interactions between the gasket/seal and the flange materials under assembly loads govern the performance of the gasket/seal assembly. A conventional linear CAE approach cannot be used because of, (a) the non-linear gasket/seal pressure vs compression characteristics, and (b) the ‘geometric’ non-linearity due to the positive sealing pressure when the gasket/seal is in contact with the flanges and lack of sealing pressure when the gasket/seal separates from the flanges. The design evaluation and optimization of (a) foam type gaskets with and without rubber beads that are common in the automotive engine, and (b) rubber seals that are common in the automotive transmission, using this approach, have been discussed.