The present invention discloses a speed transformer adaptor comprising an input shaft and an output shaft and a plurality of gear systems coaxially assembled within a casing. The gear systems individually comprise a rotatable member having a first portion forming an externally toothed sun gear and a second cylindrical portion having internal gear teeth. The externally toothed sun gear portion of each gear system is coaxially positioned within the cylindrical portion of the adjacent gear system. A pinion gear is disposed within the cylindrical portion of each gear system for engaging the sun gear and the internally toothed gear to transmit power therebetween. A clutch is provided and when not engaged allows the adaptor to function to provide high speed rotation of the output shaft with low speed rotation of the input shaft, and when slidably engaged allows the input shaft, casing, gear systems and output shaft to rotate in unison to provide a 1:1 input/output ratio. The adaptor is also reversible to provide a reduction in speed from the input speed of rotation to the output speed of rotation.