Pinion seal maintenance recommendations vary by manufacturer. Generally these seals must be replaced when leaks develop. Pinion seals should be checked and replaced whenever servicing a universal joint.
Replacement of the pinion seal usually requires removal and installation of only the pinion shaft nut and flange. Remember, a circular mounting flange, U-bolts or straps are used to hold the driveshaft in position on the differential pinion. The mounting flange attaches directly to the pinion yoke, while U-bolts/straps contact the bearing cups.
SKF recommends the following steps to achieve a successful pinion seal installation:
1. Once a new seal is selected, clean and inspect the pinion yoke seal surface.
2. Apply lubricant to the seal lips. With a seal installation tool and adapter, press the seal into the housing. The seal should be centered and seated squarely.
3. Check the pinion shaft splines and yoke for burrs or damage. Wipe the pinion clean.
4. Apply lubricant to the outer diameter of the pinion yoke and on flange splines.
5. Replace the pinion yoke on the shaft. Match previously made marks so that the shaft and yoke align.
Courtesy of SKF.