The axles don't have anything on the inside of the center section that hold them in. There are 4 bolts on the end of the axle tube that retains plate that holds the bearing into the housing. With a disc brake setup the caliper bracket is part of the plate. The bearing is pressed on the axle and the plate holds the bearing in. Once you have the plate unbolted you may have to thump the axle with a wood block and a hammer to knock it out of the housing. If the fit is real tight you might have to use a slide hammer axle puller to get it out.