Abstract: An improved mechanism is provided for biasing a driven gear in a gear train of the variable center distance type in which the driven gear is meshed with a drive gear and rotates about an axis which is not fixed, at least radially, relative to the axis of the drive gear. The biasing mechanism includes spring means engaged with the driven gear for biasing the same substantially radially toward the driven gear into mesh therewith at a force which provides appropriate relatively low-level engagement forces between the meshed gear teeth. A stop is provided for limiting deflection of the spring means in a direction corresponding to unmeshing of the drive and driven gears. The stop is positioned to limit such deflection of the spring means to an amount less than the deflection required for unmeshing of the gears.