Z4M Diff Output Shaft Seal Replacement

[yousefnjr]

Apologies for big pictures

Not a full-on guide, but I did this over the weekend and thought I would share some pics/tips. This is much easier to do if you have access to a lift, but jackstands should work too. Wheels don't need to come off.

For clearance, the diffuser and one of the panels (the metal one under the diff) need to be removed, 8mm hex.

This is what my passenger side output shaft looked like:


Remove the 6 torx bolts securing the shaft to the diff, E12 socket size. I found it easiest to remove 3, then rotate the wheel and remove the other 3. The boot on the shaft gets in the way of your tool, but make sure you have a good fit onto the bolts. Mine were pretty tight.



After the bolts are removed, wiggle the output shaft off the diff and move it over to the side. The inner splined portion of the shaft is now exposed. It pops out easily with a pry bar, but you won't have enough room to remove it without dropping the rear sway bar. Remove the 4 allen bolts (8mm I think) that hold the bushings (2 on driver side, 2 on passenger) and it'll swing down.



With the sway bar out of the way, pop out the splined portion and set it aside





With the splined portion out, the seal is now exposed. It's right on the edge of this hole. There's a special tool to remove the seal; I didn't have it and used a big pry bar. There's an inner lip made of metal on the seal itself, so make sure to pry on that and nothing else. Mine was in really fucking tight, so use your muscles!





Once the seal is out, pop the new one in and gently tap it with a hammer. It sinks in about 1/4", so make sure it's fully seated. You can put the old seal on top of the new one and tap it home.

Putting everything back together is straightforward. The torque spec for the 6x torx bolts is 100nm.

Now it's clean



This is a great time to flush the diff fluid as well. Good luck!

[bignosejim]

Nice!! Thanks for sharing.

[Vanne]

Great diy mate, excellent pics.