A three part paper to describe the results of several gear drive types with a high gear ratio is presented. A single stage planetary gear train with double helical gears is described with methods to reduce transmission errors and improve load distribution by regulating backlash during assembly. A new arrangement for face gear is also described. This new mechanism can perform rotations between axes that are collinear and intersected. Finally the design and simulation of an isostatic planetary gear train is presented. Conditions that can lead to noise and vibration of the planetary gear drive are described.Litvin, Faydor L. and Fuentes, Alfonso and Vecchiato, Daniele and Gonzalez-Perez, IgnacioGlenn Research CenterGEARS; MECHANICAL DRIVES; LOAD CARRYING CAPACITY; LOADS (FORCES); ERRORS; ROTATION; SIMULATION; VIBRATION