Abstract: The various embodiments herein provide a constant speed universal mechanical joint mechanism with crossover angle up to 90 degrees and more. The universal mechanical joint comprises an input coupling, an output coupling, at least one input shaft, at least one output shaft, a plurality of guide arms, at least three connecting arms, a plurality of connecting means, a plurality of external retaining rings and a plurality of bearings. The input coupling is connected to the input shaft and the output coupling is connected to the output shaft in such a way that the plurality of retaining rings joins each of the input coupling and the output coupling with the plurality of guide arms and the plurality of connecting means. The plurality of retaining rings and the plurality of bearings are used to connect each of the plurality of guide arms to the at least three connecting arms.