A corn head row unit gearbox includes an input shaft, that rotates about a first axis of rotation and that drives a set of gears. The gears transfer rotation of the input shaft into rotation of a gathering chain output shaft (114) about a second axis of rotation, generally transverse to the first axis of rotation. The gathering chain drive shaft (114) rotates within a bushing mounted within a frame structure of the gearbox. A bushing seal (128) has an annular mounting sleeve (150) with an inner diameter that is press fit over a boss on the frame structure.
