A gearbox assembly comprising of at least one planetary gear set comprising one or more ring gears, one or more sun gears and a planet carrier. The planet carrier supports two sets of circumferentially spaced planet gear bearings, pins and planet gears. The bearings, pins and gears are able to self adjust in an angular direction relative to the carrier supporting disc whereby the rotation axis of the planet gears may remain perpendicular to the plane of the planet carrier or skewed from said plane.