2. Remove the differential cover (see Section Removal and installation of a casing of differential).
3. Apply paint or scraper alignment marks (indicated by arrows) on the flange, pinion shaft and pinion shaft nut to ensure proper assembly.
4. Remove the stop plate, then hold the inlet flange stationary and loosen the flange nut.
5. Using a puller, remove the inlet flange.
If the gear shaft has been grooved where it contacts the old oil seal, consult a qualified technician for further action. A new pinion shaft bushing may also be required.
6. Remove the old oil seal with a special tool or a large screwdriver. Make sure you don't scratch the oil seal seat.
7. Dip the new oil seal into the differential oil. Set it in place, jaws inward, using a large replacement head or a piece of pipe.
8. Lightly grease the input shaft and press the input flange onto it, but do not try to seat it all the way. Screw on the flange nut and, using a torque wrench, slowly tighten it, noticing the force at which the marks are aligned - it should be close to that specified in Table of sizes and adjustment data. If the force required to align the marks is slightly less than required, it is possible that the gear shaft bushing needs to be replaced. Because this job requires special tools and relevant experience, it is better to leave it to the specialists of the BMW dealer or workshop.
9. If the required force is reached before the marks are aligned, do not continue to tighten the nut until they are aligned.
Do not tighten the nut after aligning the marks and vice versa, as this will lead to pinching of the gear shaft bushing.