Abstract A graph-based technique to simulate and analyze parametric influences in torsional systems is presented. The system properties such as polar inertia, torsional stiffness, are represented by a directed graph. The theory of qualitative and quantitative influences is used to develop a technique which predicts the direction of change and accurate estimates of parametric values. Both qualitative and quantitative estimates provide important clues (direction of change and the estimated quantitative change) to vary parametric values. This technique is especially useful for estimating parametric influences on the overall system response and for generating a number of alternate design options. This is complementary to classical methods and conventional finite element method and is validated through examples related to free vibrations of torsional systems. Results presented here show that the estimates obtained using the proposed technique are more accurate compared to those obtained in previous research. Future directions in the context of complex design reasoning systems are also highlighted.