The carrier bearings on the differential support the ring gear and carrier and allow it to spin smoothly. These bearings also need a tight preload to reduce sideways ring gear movement under load. Some axles have adjuster rings to set preload more easily, but our Dana 44 uses shims. The shims often go between the bearings and the open carrier or locker on the bearing journals. The ARB Air Locker uses specific bearings and the shims between the race and the housing, so we started by pressing the carrier bearings onto the locker.