There are several benefits to using composite materials for gears made of Polyamide 66 (PA66) reinforced with Short Carbon Fibre (SCF). It includes lightweight construction, enhanced strength, noise reduction, and increased resistance to wear and corrosion. This study investigates the mechanical properties of PA66 composites with varying fiber contents, specifically examining the tensile, flexural, compression, and density of specimens. This study also investigates the manufacturing process of composite spur gears and employs analytical methodology to ensure design robustness under varying loads. The torque and the twisting angle of the spur gear have been evaluated using an analytical approach. An experimental approach was used to determine different types of torque are 37, 19, and 28 Nm, and the twisting angles are 8.5, 17, and 28 degrees respectively. Then the life of the composite gear pair was estimated at 2x10^9 cycles by analytical approach. Despite the failure of the parameters, the results were deemed to be satisfactory. Further, the analysis extends to the examination of failed gear teeth using Field Emission Scanning Electron Microscopy (FESEM). The knowledge acquired offers insightful recommendations on the durability and usability of composite gears under various operating circumstances. Their findings were corroborated through rigorous experimental assessments.