Abstract: A hybrid gear drive suitable for the transformation of motion and power between an involute worm and a face gear wherein the axis of the face gear and the worm may be crossed or intersected. The gear drive includes a multi-thread involute worm in meshing engagement with a face gear having helical teeth. The multi-thread involute worm threads each have a driving surface and a coasting surface formed in the profiles of the involutes of a pair of base circles having different radii. The gear drive allows practical gear ratios up to about ten for high speed, high load applications such as helicopter or automobile gearboxes.