The axle housing is the outer enclosure of the axle shaft. It protects the inner shaft from damage and may contain lubricant. On rear wheel drive the axle housing includes the differential gears in the centre of the axle.
The axle housing may be a bulky cast structure or a mix of cast and steel tube.
If the axle is damaged this can lead to malfunction of the whole axle assembly. The axle housing functions to protect the axle and associated components by shielding them from impact and preventing water, dirt and dust from penetrating these parts.
The axle housing can suffer from general wear and tear and will need to be replaced if it rusts, cracks or splits. The axle housing is specifically manufactured for the make and model of your vehicle.