A cotton harvester row unit includes belt drive and a variable transmission to reduce noise and optimize spindle and doffer speeds of rotation while permitting spindle drum structure rotational speed to change with changes in harvester speed. In one embodiment, a variable speed motor drives the ring gear of a planetary gear set to vary the ratio of spindle and doffer speed to drum speed. The planetary gear set may be enclosed to also help reduce noise and to decrease grease consumption. Nearly constant spindle and doffer speeds may be maintained over a wide range drum rotational speeds, and the upper speeds may be limited to avoid operation above critical speeds of components. The transmission may be configured to reduce or completely eliminates gear meshing off of the drum centerline to thereby reduce row unit manufacture precision, and a relatively low power motor may be used to adjust the ratio of spindle and doffer speed to drum speed.