Abstract: A cotton harvesting unit with a cotton doffer assembly rotatable about a vertical axis and including an adjustable drive unit with a vertical drive shaft for imparting rotary motion to and for vertically positioning doffer pads of a doffer unit relative to picker spindles of an adjacent picker rotor. The drive unit vertically positions the doffer pads through an operative mechanism rotatable about a second axis adjacent to the doffer assembly. A motion converting mechanism converts rotary motion of the operative mechanism into linear motion of the drive unit drive shaft. The drive shaft of the drive unit and doffer unit are releasably interconnected to each other to facilitate repair/replacement of the doffer unit. To inhibit contaminants for encumbering adjustment of the drive unit, the motion converting mechanism is wholly arranged within the housing assembly and protected from the ambient environment in which a harvester is operated.