A gearbox repair assembly is disclosed herein. The gearbox repair assembly includes a sleeve having an inner diameter configured to receive a bearing assembly and an outer diameter configured to fit within a bore of a gearbox housing. The gearbox housing can be part of a gearbox of a wind turbine. The gearbox repair assembly further includes a retaining plate configured to be attached to the gearbox housing for preventing an outer race of the bearing assembly from rotating in the bore relative to the gearbox housing. Also provided are methods to repair such a gearbox. The gearbox repair assembly and related methods reduce the time and cost needed to repair the gearboxes.