Loosen the wheel lug nuts, raise the rear of the vehicle, and support it securely on jackstands while blocking the opposite set of wheels to prevent rolling. Remove the wheels and disconnect the driveshaft from the differential companion flange, fastening it out of the way. Mark the relationship of the pinion flange to the shaft and count the number of exposed threads on the shaft. A flange holding tool is needed to keep the companion flange from moving while loosening the self-locking pinion nut, although a chain wrench can also be used. Remove the pinion nut and withdraw the flange, using a two-jaw puller if necessary, avoiding any prying or hammering behind the flange or on the end of the pinion shaft. Pry out and discard the old seal, then lubricate the lips of the new seal and fill the space between the seal lips with wheel bearing grease before tapping it evenly into position with a seal installation tool or a large socket, ensuring it enters the housing squarely and to its full depth. Install the pinion flange, aligning it with the marks, and if necessary, tighten the pinion nut to draw the flange into place without hammering. Finally, install a new pinion nut and tighten it to the specified torque, completing the installation in reverse order of removal.