In this article, the torsional vibrations of a transmission system installed on a test rig are investigated. The transmission system comprises a Dual Clutch Transmission (DCT) and a Manual Transmission (MT) interconnected via their output shafts. The excitation of the dynamic system is performed by two electric motors which ensure an accurate control of the speed or torque. The analysis includes the measurement of the external torques, applied by the two electric motors to the mechanical system, and the measurement of the system response in terms of angular speeds at different positions along the transmission line. The frequency response of the system is estimated from the experimental data and compared with the simulation results of a 4-DOF lumped parameter model, which proved adequate to describe the dynamic behavior of the system up to a frequency of 100Hz. A good match between simulation and experimental results is shown. Therefore, the model can be used to predict the torsional vibration of the transmission system under test when it behaves linearly.