For rack & pinion applications requiring ultra-precise positioning and repeatability, the system backlash can be eliminated by using two pinions - one to drive the axis and one to "preload" the axis to remove the backlash.

The simplest zero-backlash rack & pinion drive utilizes a split-pinion. A split-pinion consists of two pinion halves and an axial spring pack. The pinions halves mesh with opposite tooth flanks on the same rack, eliminating the backlash. The axial spring pack is used to preload the rack & pinions to insure that no backlash develops during the operating cycle.