This invention relates to a fastener driving device including a variable ratio gear mechanism that enables the ratio of the rotation of the handle to the rotation of a driving bit extending from the handle to be varied to allow the bit to rotate at different speeds from the handle. The device includes a gear mechanism disposed within a housing for the device that includes a locking member and a biasing member. The biasing member urges the locking member into engagement with the gear mechanism to lock the gear mechanism in a configuration for a 1:1 gear ratio. A selector switch is secured to the device over the gear mechanism and is operable to move the locking member into and out of engagement with the planetary gears against the bias of the biasing member to provide an increased gear ratio for the gear mechanism when desired.