An All-Wheel Drive Transmission system powered by a 10 HP Briggs & Stratton engine is designed for a single-seater all-terrain vehicle. Because of the engine power limitation, it's important to reduce the vehicle's weight and improve its performance. The aim is to increase the traction of the vehicle and it must be able to climb high grades, cross slippery mud pools, and snow tracks with minimum drive slip. While performing, the system must be reliable and not fail under any circumstances. The study focuses on the optimized calculation of engine performance, vehicle mass, air drag, rolling resistance, continuously variable transmission (CVT) shifting, gearbox reduction ratio, gear selection, shaft, and casing. The design and analysis process includes the development of a compound gear train with gears having a minimum diameter and face width, to lower the rotational inertia of the system and included the calculation of static failure from contact and bending stresses, gearbox housing, shafts, and bearings. All components are designed in Solidworks 2016 and analyzed in Ansys Workbench 19.2.