In this work two methods for gear-rattling detection in mechanical systems are studied. For this purpose, an experimental quick-return mechanism was constructed with gears driven by an electric motor. Rattling is detected from the mechanical vibrations acceleration and the electric motor current. Vibrations signal is measured by a biaxial accelerometer and electrical current is obtained from the motor electronic driver. Signals are processed in time-domain and time-frequency domain. Rattling level is measured through a proposed performance evaluation index that is obtained from the application of band-pass filters and the RMS value of the signal for the time-domain processing. For the time-frequency analysis, the wavelet transform is used to isolate the rattling and the signal is post-processed to compute the RMS value. It is shown that the use of the electric motor current for the detection of rattling produce better results than the mechanical vibrations acceleration. With respect to the time-domain method versus the time-frequency method, it was found that the application of the wavelet transform significantly improves the indexes that are used for gear-rattle detection.