Hi, There is a rattling noise in one of the automobile passenger car gearboxes that we designed. After few experiments and observations, it was found that the noise is because of incorrect clutch stiffness and hysteresis behavior. I have got some fundamental questions about both: 1. Clutch stiffness Vs rattling: I understand that higher the stiffness of clutch, lower the relative displacement between crank shaft and transmission shaft for a particular torque. All infiltrated fluctuations to the clutch will be absorbed to an extent. And this is done by the springs in the clutch. But, won't the springs start vibrating (as it is an elastic body and not a dampening member) after they absorb this fluctuating forces? What is better for rattling - High stiffness clutches or low stiffness clutches? 2. Clutch hysteresis Vs rattling: [/SIZE][/IMG] The attachment shows the hysteresis values of the clutch that I am discussing here about. The unit is NM. What exactly does this hysteresis torque physically mean? How is hysteresis responsible for gearbox rattle? Thanks a lot!