An speed reducer assembly is provided along with a method and apparatus for adjusting the speed reducer assembly to achieve zero backlash. The speed reducer assembly includes a split worm with a fixed worm segment and a floating worm segment which mesh with the teeth of the gear. The position of the worm relative to the gear can be precisely and accurately adjusted without disassembly of the speed reducer or removal of the speed reducer assembly from the housing. Elimination of a constant spring force on the floating worm segment of the split worm also provides for the elimination of drag which results in a speed reducer assembly with increased efficiency. The elimination of drag also reduces the wear on the elements of the speed reducer assembly.