An embodiment is a seat height gear system including a monopost apparatus configured to be mounted under a seat, the monopost apparatus comprising a lower post and an upper post, and a direct drive motor apparatus within the monopost apparatus, the direct drive motor apparatus including a motor and a gear unit, the gear unit including a pinion and a rack bar, the rack bar being configured to be engaged with the pinion, the motor being fixed to the lower post of the monopost apparatus, the pinion being coupled to the motor, the rack bar being fixed to an upper post of the monopost apparatus, the motor being configured to rotate the pinion, and the rack bar being configured to convert the rotation of the pinion into the linear motion.