BMW E46 325xi 330xi Front Differential Seal Replacement DIY

In this article I will show you how to replace a front differential input shaft seal on BMW E46 01-05 325xi and 330xi.  If you also need to replace the output shaft seals please see my other articles on changing the axle boots.  Replacing the input shaft seal isn't a very complex job but due to space limitations it is definitely not my favorite.  To complete this job you will need a thin walled 30mm socket, gear puller and a seal driver.  Seal driver set and a gear puller can be rented from most part stores if you don't own them.  As for the parts, you will need a new pinion seal 31521428678 and a new locking plate  23211490120.

1.  Start out by removing all of the under panels.  Drain the differential oil.  You can skip draining the fluid, let some spill out when you remove the seal and add more after you are done but not draining the fluid makes the job messy and stinky. 

2.  Unbolt the front drive shaft.  If you don't have a helper who can hold the brake pedal depressed pull up the parking brake and unbolt two bolts from the differential and two bolts from the transfer case.  Release the parking brake, rotate the drive shaft.  Pull up the parking brake again and unbolt the remaining 4 bolts.  

3.  Once the drive shaft is out of the car you need to mark the position of the differential flange nut.  There is no specified torque setting for this nut, it has to be reinstalled in the same position as it was before.  If you over torque this nut the the collapsible sleeve on the input shaft will collapse and you'll end up with a noisy differential because the gears won't be properly aligned.

4.  Using a screw driver or something sharp remove the locking plate.

5.  Have someone hold the brakes and unbolt the flange nut, or use an impact wrench.  

6.  Using a gear puller, pull off the differential flange.

7.  Use a seal puller to pull the old seal out of the differential housing.

8.  Install a new seal using a seal driver, reinstall the flange, torque the nut down so the marks you made on the input shaft and the nut align.  Don't forget to fill the differential with fluid.  At first it might feel like the input shaft is hart to turn but don't worry, after driving for a bit everything will be back to normal.