The brake casing (axle housing) unbolts from the differential housing. The L39 has a large extra frame that will need some unbolting to get it apart. Is your brake casing broken?
I have an L4310 and have done this within the past year. The brake casing is a separate case that is bolted to the diff. The axle housing bolts to that. It was not too difficult, but the parts are a bit heavy, so be careful.