A model-free controller for the full semi-active suspension system of a pick-up truck is proposed. The controller is focused in the passengers comfort and stability of the vehicle. A Combinatory quasi-Optimum Damping (COD) controller defines the best combination of damping force by analyzing the frequency response of the vehicle for all possible combinations among the semi-active dampers. The solution is defined in bandwidths by using a frequency estimation module of the road profile based on a Kalman filter. A model in CarSimTM was used as Software-inthe- Loop (SiL). The semi-active suspension system is composed by four experimentalMagneto-rheological (MR) damper models. Simulation results show the controller benefits in comfort in the Bounce Sine Sweep (BSS) test, specially at frequencies close to the resonance frequency of the sprung mass (reduction of 50%). In the Double-Lane Change (DLC) test, the COD controller improves the roll control by reducing 28%the roll rate and 21%the roll angle. For the FishHook (FH) test, the improvement is highlighted in the vehicle slip angle (reduction of 26%); however, the transient response of the yaw angle, yaw rate and lateral acceleration is better when the COD controller is used because the oscillations have lower amplitude with shorter settling time. Copyright © 2012 by ASME.