This paper studies the design and selection of the reduction ratio to be used in the transmission of a solar powered vehicle. A single degree of freedom vehicle model is presented in which the equation of motion for the longitudinal direction is obtained. The equation may be expressed in the form given below: Where PTractive is the tractive force produced at the tire ground contact; ma is the inertial acceleration force; FR is the sum of all forces, of first order magnitude, contributing to rolling resistance and Fa is the aerodynamic resistance force. The equation may be expressed as a function of the reduction ratio, characteristics of the motor (rpm), available acceleration, wheel and tire used. This problem was solved by iterative methods using a spreadsheet. When the acceleration is zero the maximum velocity may be obtained. When the the velocity tends to zero the maximum torque is determined. This however, is constrained by the power characteristics of the motor. Using the estimated solar energy available to the vehicle at the motor, graphs of maximum velocity and motor efficiency vs reduction ratio were made. From these plots it was determined that at lower power consumption [.745KW (1 hp), 1.49 KW (2 hp) ] a ratio of 3.7:1 is best suited.