Does the axle have to be removed change rear wheel bearings on a 99 Chevy Siverado 2wd?

No, you generally do not have to remove the axle to change rear wheel bearings on a 1999 Chevy Silverado 2WD. The bearings are typically pressed into the axle housing, and you can access and replace them without removing the axle. You will need to remove the backing plate, rotor, and likely the hub assembly to get to the bearings. However, the axle shaft itself remains in place.