Remove the axleshaft. Screw off the end of the axle housing and pry the oil seal off with the aid of a seal removal tool. Squeeze a layer of multi purpose grease on to the housing recess where the new oil seal is to be fitted and then gently pound the new seal into the recess the lips inwards and the metal face visible from the end of the axle housing using a hammer, seal installation tool, large socket or piece of pipe. If properly fitted the face of the oil seal should be butting on the extremity of the axle housing. Install the axleshaft.