Main Gear Seals — Replacement (BMW 3 Series E46)

Input shaft seal

Note: You will need a new flange nut retaining cap during installation.

1. Drain the oil from the final drive (see paragraph 10).

2. Remove the main gear unit (see paragraph 2) and clamp the knot in a vice.

3. Remove the locking cap and mark the relative positions of the nut, flange and input shaft of the main gear (Fig. 3.3). Discard the cap, as you will need a new one during installation.



4. Screw a steel strip to the flange to prevent the flange from turning. Unscrew the flange fastening nut, counting the number of turns to remove the nut.

5. Using a suitable puller, remove the flange from the shaft, then remove the boot. If the boot shows signs of wear, replace it.

6. Use a screwdriver to pry up the input shaft seal. Clean the seating surface under the seal.

7. Lubricate the lip of the new seal, then press it flush with the outer surface of the housing. Use a piece of pipe of the appropriate diameter for pressing.

8. Put on the boot, then install the flange, aligning the marks made before removing it. Screw the nut the number of turns counted earlier and align the marks on the nut and flange.

Caution! Do not overtighten the flange mounting nut. If you overtighten the nut, the spacer washer located behind the flange may become deformed. In this case, the washer will have to be replaced. This will require disassembling the main gear (see paragraph 1).

9. Secure the nut with a new lock cap.

10. Install the main gear in place (see paragraph 2), then put oil in it (see paragraph 10).

Output shaft seals

Note: When installing, you will need new bolts for fastening the drive shafts to the final drive flanges, as well as spring rings for fastening the final drive flanges.

11. Drain the oil from the final drive (see paragraph 10).

12. Remove the bolts securing the input shaft to the final drive flange. Secure the end of the input shaft with wire. Note: Do not allow the input shaft to hang under its own weight as this will damage the constant velocity joint.

13. Using a suitable lever, remove the flange from the final drive. Be careful not to damage the boot or the final drive housing (Fig. 3.13). Remove the flange, then remove the boot. If the boot shows signs of wear, replace it.



14. Carefully remove the cuff from the main gear housing. Clean the seating surface under the cuff.



15. Remove the flange retaining ring from the splined shaft (Fig. 3.15).



16. Install a new snap ring. Make sure the ring fits into the groove of the shaft.

17. Apply a little oil to the edge of the new seal and press it into the main gear housing until it stops. If necessary, use a piece of pipe of a suitable diameter (Fig. 3.17).



18. Put on the boot, then insert the flange. Make sure that the flange retaining ring is in place.

19. Align the drive shaft with the final drive flange, insert new flange mounting bolts and tighten them to the specified torque.

20. Fill the final drive with oil (see paragraph 10).