A method of constructing a shaft seal assembly includes attaching a PTFE seal element to an outer metal case and disposing a bore of the PTFE seal element onto a mandrel. Then, heating the PTFE seal element while on the mandrel. Further, cooling the PTFE seal element while on the mandrel and, removing the shaft seal assembly from the mandrel. The resulting seal element provides a reliable seal against a running surface of a shaft in use, while at the same time producing low running torque against the running surface of the shaft. Further, a minimal axial push force is required to install the shaft seal assembly onto the shaft, thereby reducing the potential of damage to the seal element or inversion of the seal element during installation.