Rear lower control arm replacement - Move Diff?

[seismic22]

Hi all,

Having been under the car tonight, Im fairly sure I have spotted that my driver side rear lower control arm is bent slightly upwards. Doing some research on the internet doesnt reveal any Z4 specific DIY's on replacing the arm however it does highlight a couple for e36 and e46's. It seems for the e36 and e46 the differential needs to be partially unbolted and moved back an inch to enable the arms inner bolt to be removed.

Can someone confirm if the differential needs to be slid back an inch on the Z4 to enable a control arm change?

Cheers

[MJJamieson]

I was considering changing mine but access looks restricted to remove the bolt, as there the same subframe I would say yes, im leaving mine!!!

PS. As this is your first post I would quickly say something in the newbies section and add some photos before the forum police turn up.

[seismic22]

Ok so I changed the control arm at the weekend and thought I would post about it to help others in the future. Its short and sweet I'm afraid as I am struggling with time but I thought it best to post something rather than nothing.

My control arm had the slightest of bends in it and this could have been compensated for with alignment. I didnt like the fact it was bent and that it was possibly a weakness in the arm however so I became intent on changing it.

Reading around there is very little about changing these arms on the internet, most that is out there refers to e36 and e46's. The only set of instructions I found for the Z4 suggested it was hard work and that the diff would need moving back 1 inch. This was not the case for me. Below is how I changed the arm in sub 2 hours. It was relatively straight forward and I suggest most people could do it in an afternoon / morning even with limited mechanical skills.

Jack up the car up on all four corners and place securely on axle stands.

Remove the heat shield from below the diff/centre of the car.

Remove outer bolt where the arm bolts to the hub, this is the camber bolt used for adjusting the rear camber.

Slacken the front two diff bolts 10 - 15mm only.

Loosen the inner bolt and see how the bolt cannot be removed due to the driveshaft being in the way.

Get a pry bar or some other sort of lever and at the front of the diff find a location to lever the diff back just a few mm until you can wiggle the inner bolt free from the control arm. This is a little fiddly and a second person helping at this point is useful.

Fitting the new arm is the reverse of removal (you will need to lever the diff back again a few mm) just make sure that the camber bolt on the outer end of the arm ends up in the same position as before. This will ensure that the rear camber is not hideously out whilst you subsequently drive to where you get your alignment undertaken.

Guides for the e46 and e36 suggested you needed to remove the rear diff bolt aswell to enable you to lever the diff back. This wasnt the case for me and certainly save me a lot of time.

Other thing to note is the arm I changed was the offside (right). The exhaust runs on the left side of the car so if you are changing the left arm, access might be more tricky.

Hope this helps.

[MJJamieson]

Nice one, handy to know for the future.

[GuidoK]

This is pretty much the same method as how it is written in TIS. (TIS only suggests to also loosen the rear diff bolt, and for that you have to loosen the rear stabilizer bar brackets)

And I guess you also have to remove the exhaust to be able to remove the heatshield
Thats probably the most labour intensive part.