DIY for rear upper control arm (wishbone)? E46 M3 vs. other E46?

[M3Bob]

Was refreshing the rear suspension and discovered that my wishbones are cracked...looks like i waited too long to install the reinforcement plate and/or replace the shocks. Found a DIY on youtube where the wishbones were being replaced on a 3-series and it looks fairly straightforward...my question is whether the geometry for the M3 makes getting to that bolt by the differential any more complicated.

aaaaaand the shop stripped out (and didn't anti-seize) the set screw on my adjustable spring perch. Not having a good wrenching day.

[sdwz_m3]

I actually just finished this job. I replaced all the bushings/bearings that attach to both control arms. You’ll need to pull the differential out. I was able to do it without disconnecting the exhaust


Sent from my iPhone using Tapatalk

[heinzboehmer]

I'm in the middle of this too. And yeah diff needs to come out. If you're really feeling lazy you can remove the diff without removing anything else. You kinda have to squeeze around some of the plastic under tray things, but it's doable.

[M3Bob]

I eyeballed the angles while putting everything back together so i could roll the car into the garage...i -think- I can get those things out without dropping the diff. That said...i do need to replace the diff bushings, so might be a good opportunity to do that. Any tips on removing the diff without yanking the exhaust?

[heinzboehmer]

I eyeballed the angles while putting everything back together so i could roll the car into the garage...i -think- I can get those things out without dropping the diff.

The bolts for the upper arms hit the diff before they can be completely removed, so you do have to drop it to change them.

There's an access hole in the heat shield that lets you get to the bolts that hold the driveshaft to the diff. A couple swivel sockets/extensions will let you get to all the bolts without removing the exhaust or anything else.

[M3Bob]

The bolts for the upper arms hit the diff before they can be completely removed, so you do have to drop it to change them.

There's an access hole in the heat shield that lets you get to the bolts that hold the driveshaft to the diff. A couple swivel sockets/extensions will let you get to all the bolts without removing the exhaust or anything else.

Dammit! The devil is always in the details....Thanks!

[01SG]

You do not have to completely remove the differential. Just like for the camber arms, you can remove the inner upper arm bolt by merely taking out the three differential bolts and manipulating it around, there is enough play to make room. It's a lot less effort than dropping the entire differential; no need to take off the axles, driveshaft, or exhaust. Of course it's easier once the whole thing is out of the way, so if you need to do bushings anyway, by all means..

[heinzboehmer]

Yup. I was completely wrong. I took the top arm off with the diff still in the subframe literally five minutes ago. Didn't have to loosen the diff bolts or anything. Granted, my subframe is currently off of the car, so it might be a bit harder with it still installed, but it looks doable.

The lower arm bolt definitely hits the diff though.

[M3Bob]

I have a vague recollection of wiggling the diff around on a jack (with input and output shafts still attached) when i replaced my lower arm years ago.....

[heinzboehmer]

Quick update. Finished taking my subframe apart today and here's the deal.

On the passenger's side, the bolts for both the upper and lower arms that attach to the subframe can be taken out without touching anything else. On the driver's side, both bolts hit the diff when being removed. You can remove the three diff bolts (no need to remove input or output shafts) and wiggle the diff around to get the driver's side bolts out.

[enjoy_m3]

In my experience, getting the bolt back in is more difficult than taking it out without completely removing the diff. If you have the exhaust and drive shaft out, it's much easier to drop the whole subframe and change it out. I ended up using offset bushings onthe upper arm and it gave me more camber for more aggressive track alignment. It was a good budget alternative to camber arms.

[M3Bob]

the driver's side is giving me fits. I've lowered the diff as low as it can go without removing it and it's still proving extremely challenging to get a socket on the bolt that sits right above the output shaft. i'm -this- close to just doing the passenger side and taking it to a local shop to have them worry about the other one.

[01SG]

Did you pull the differential back completely? I think it's less about lowering it and more about pulling it back-it will go pretty far. Are all three bolts completely out?

Your problem might just be trying to use a ratchet and socket. Use a normal wrench. If you want to torque it to the precise 81 ft lbs, then you will probably need to remove the differential.

[M3Bob]

Did you pull the differential back completely? I think it's less about lowering it and more about pulling it back-it will go pretty far. Are all three bolts completely out?

Your problem might just be trying to use a ratchet and socket. Use a normal wrench. If you want to torque it to the precise 81 ft lbs, then you will probably need to remove the differential.

Hmm, no i didn't try that. And yes....been trying to get an 18mm socket on there. I'll give it another shot and see what happens.....

[01SG]

It is a lot easier with the differential out. But still not that much easier!