This paper aims to propose an experimental method to detect and quantify the existence of cracks in spur gear teeth using modal analysis. Frequency Response Functions FRFs obtained analytically in previous work are considered to be validated experimentally in the current work. The analytical method using FRFs, which were applied in Ref. [28] for certain crack sizes, is validated here experimentally by using hammer test and measuring the vibration response of a neighbouring tooth. The results obtained from the modal analysis testing shows a considerable response peak deviation from the original peak location of the healthy case. The deviation becomes more for bigger crack sizes. This experimental result, using the method developed and explained in this work, validates the analytical method applied previously using FRFs.