Rear Lower Control Arm Replacement

[tominizer]

Going to have a go at this *BIATCH* and I hear it's a bit of a pain in the arse crack....... especially the drivers side due to the diff. There seems to be NOTHING documenting the labourious nitemare. I will try and see what I can post up and take some pictures.

I will be doing this in my garage (no lift) with DIY-er tools........ laying on my back..... likely cursing.

IF anyone has found a good resource for this job, please do link it. I'm going to have a look at the BMW E46 forums this evening to see if there is anything.

[AK72]

this should help
https://blog.bavauto.com/14044/bmw-e...ll-how-to-diy/

[tominizer]

The driver's side looks to be a real bear on the Z4M. The diff on these cars is setup differently than the e46 3-series, although I still want to check the E46 M3. they keep talking about "jimmy-ing" up the diff after loosening up the two top bolts and removing the third if memory serves me right. On our Z4M there looks to be a bolt to the subframe on the passenger side at the front and two higher up on the rear. That front one does not look easy to access either.

And from eye-balling it, even if the diff was loosened up, there doesn't look to be enough vertical to push it up to give room to remove that driver's side bolt in the lower camber arm as there's subframe up there in the way.

I've also heard about loosening up the diff and with a pry bar, moving it towards the back of the car. I assume that means the driveshaft has to be released and the diff moved backward on a jack. But I don't know.

I'm still digging through this and not seeing the light yet without taking a LOT of parts down. There has to be an easier way or the designer needs to be shot.

[tominizer]

Spent another hour or so poking around the internet and "sleeping" under the car looking up at this setup. The driver's side diff mounting bolt on the back....... even if the entire diff was loose, has barely a finger width of play to move upwards. So I don't think that this is possible like is done on the E46 cars. The only thing I can think of now is side to side play but I still don't believe there is going to be enough room to get those bolts out.

I'm sadly believing the diff may have to come out........ but I don't want to believe it. I wish someone could chime in here that's been down this road and advise. It has to have been done of course as people have aftermarket lower control arms........ but I just can't find any instruction anywhere on the install.

[F360C]

Originally Posted by tominizer

Spent another hour or so poking around the internet and "sleeping" under the car looking up at this setup. The driver's side diff mounting bolt on the back....... even if the entire diff was loose, has barely a finger width of play to move upwards. So I don't think that this is possible like is done on the E46 cars. The only thing I can think of now is side to side play but I still don't believe there is going to be enough room to get those bolts out.

I'm sadly believing the diff may have to come out........ but I don't want to believe it. I wish someone could chime in here that's been down this road and advise. It has to have been done of course as people have aftermarket lower control arms........ but I just can't find any instruction anywhere on the install.

I just put in new arms but I had the subframe out to do it. I am pretty sure you can replace the arms without fully removing the diff. You would need to at least at remove all three bolts holding the diff and also the bolts for the drive shaft to the diff. This should allow you to slide the diff back and tilt it down a bit to the left or right. It will be tight but I think you can get the bolt out then. At this point you're only the 12 torx bolts away from just disconnecting the axles and just removing the diff fully which might just be easier.

The front bolt on the diff is easy to get to and so are the rears when the exhaust is removed. Just make sure you have a ratcheting 12 point wrench for rear diff bolts. They are a external torx but the space is tight so you use the torx socket to break the bolt loose then a ratcheting 12 point to get them fully out.

[tominizer]

Ok, how about some pictures!! Everyone likes pictures.

First Picture:

Wheels off, exhaust removed, heat shielding down and all the other junk as shown. Blue arrows sort of point out where to look for the diff mounting points. Two on the top back and one on the passenger front.

Red arrows note the passenger side rear lower control arm mounting points.

Yellow arrows note the two upper exhaust bolts that will make you want to kill yourself. More on that..... next

[tominizer]

picture 1 that didn't attach.

Also looks to be some sort of leakage/spray off the driveshaft onto the fuel tanks that I need to look closer at to see where that is coming from........ both sides.

[tominizer]

Picture #2

This little guy I used to remove the top exhaust bolts that are painful to get to (yellow arrows on the previous picture). Just slip him over and hold it there as it will not turn eventually as it presses up against the exhaust wall/flange area and Bob's your uncle

[tominizer]

Another look at the control arm pointing out the attachment points with red arrows.

[tominizer]

This is a shot of the worst part of this. The bolt attaching the control arm to the subframe on the driver's side. Red arrow is points to the bolt and the yellow star is the tiny gap you are left with to remove this bolt. There is absolutely no room. This is why I've had to pull everything down on the back end on this car making what should be a 20 min job into a huge marital affair.

The passenger side is a bit better but still a problem.

[tominizer]

Here's where I'm at right now. I'm going to remove the two upper bolts on the back of the diff and the one bolt of the front passenger side. Then disconnect the main drive shaft from the diff in hopes of being able to move the diff backwards enough.

A few things to note here. A socket and wrench do not fit to get those rear upper diff bolts out as there is a subframe support wall just behind the diff and makes the gap too narrow (see yellow arrows). F360C's notes above are 100% correct. I got the first one out using an 11mm ratcheting wrench. Second guy on the drivers side is not cooperating and I don't want to strip the head off. So off to the tool store to look for options.


Anyways, hopefully heading in the right direction here. What a stupid pain in the arse.

And on a funny/sad note, wish I had the $5K CAN to do the 4.10 diff while I'm in here. Such a tease. Sucks to be poor.

BTW, not sure why there's a red-ish tint to my pictures. I live in Canada and not the red sands. Also you'll note that the underside of my ride is NOT pristine. She's a driver, not a princess !!

[Steeler]

tominizer check the boots on the halfshafts. That "spray" on the tanks may be the start of those deteriorating/cracking and flinging the internal bearing grease.

[tominizer]

If anything, coming off the main driveshaft, not the halfshalfs. I'm seeing it (as in picture #1) forward of the diff. So this diff may have to come down at the end of the day regardless.

[F360C]

Originally Posted by tominizer

Here's where I'm at right now. I'm going to remove the two upper bolts on the back of the diff and the one bolt of the front passenger side. Then disconnect the main drive shaft from the diff in hopes of being able to move the diff backwards enough.

A few things to note here. A socket and wrench do not fit to get those rear upper diff bolts out as there is a subframe support wall just behind the diff and makes the gap too narrow (see yellow arrows). F360C's notes above are 100% correct. I got the first one out using an 11mm ratcheting wrench. Second guy on the drivers side is not cooperating and I don't want to strip the head off. So off to the tool store to look for options.


Anyways, hopefully heading in the right direction here. What a stupid pain in the arse.

And on a funny/sad note, wish I had the $5K CAN to do the 4.10 diff while I'm in here. Such a tease. Sucks to be poor.

BTW, not sure why there's a red-ish tint to my pictures. I live in Canada and not the red sands. Also you'll note that the underside of my ride is NOT pristine. She's a driver, not a princess !!

I forgot to add... Its not the norm but I usually take the exhaust off as one piece. I unbolt it at the headers and remove the exhaust with the hangers stil attached. I do this because I find it easier to get to the front 4 bolts that hold the exhaust to the headers then trying to get to that bitch of a bolt on top of the xpipe. Also since I leave the exhaust hangers on the exhaust I dont have to mess with realigning the exhaust tips when I reinstall the cans.

As far as getting the one diff bolt out.. I cant see if its hitting the frame of the car or the sway bar? If its the frame you might be able to loosen the bolts for the subframe and slide it down a bit. I think you could get it down a 1/4 inch with out fully removing the bolts

[wdb]

Originally Posted by F360C

I forgot to add... Its not the norm but I usually take the exhaust off as one piece.

^^^^ This. I didn't really read up on the "right" way to drop it, but those bolts in the center looked like too much trouble so I just dropped the whole works. Although I chose to leave the mufflers hanging in place; I thought it was easier to reattach the pipes at that point rather than undo/redo the hanger bolts.

[tominizer]

Job is done and the lower adjustable control arms are in. A few notes:

• That bolt on top of the exhaust x-pipe area is not too bad to get undone if you use that piece of tool I showed earlier. I took the exhaust down from the x-pipe back to the tips.
  
• The main drive shaft has to be unbolted at the diff.... 6 bolts.
  
• The diff has to be unbolted completely from the subframe in all 3 places and the bolts taken right out so you can shift it backwards. Use a nice thick and long flathead screw-driver to prop up the diff on the subframe when removing these bolts as that diff is heavy.
  
• The chassis reinforcement bars and plates all have to come out. They just all get in the way. I left the driver's side in as a safety for that loose diff but it just got in the way. So out came the 2x6 lumber with a jack as needed.

All the above makes access to all the necessary lower control arm hardware really easy to get at AND...................passenger side bolt comes out super easy.

BUT the driver's side is still a biatch. It does come out but you have to play with it a lot (or a little if you get lucky). Diff has to be moved right back up against the body/sway bar and jostled left and right a bit. Eventually you will get there. BUT, you will want to kill the dumb-arse F*ker that designed this thing. This should be a 20 min job from wheels on the ground to finish. It's absolutely insane that this much work has to be done to get this done.


On another note, I was unable to find any documentation on this job ANYWHERE for the Z4M. So I hope that what I've posted here does help someone and let me know if I left anything out or more info is needed somewhere. This wasn't a precise walk-thru with a tools list, etc..... that I know. But reality is that it's do-able but you may hate it. And ALWAYS when working under your car, think SAFETY FIRST. I had redundant jackstands and always thought through thoroughly about what I was going to do before grabbing tools. Car isn't worth your life or getting badly hurt over. And also, if you car is anything like mine, a pile of crap falls of the underside, so wear some protective glasses !! Anyways, have fun. DIY-ing brings a lot of satisfaction to ownership........ even if you break shit once in a while !!

[wdb]

Nice work! Glad to hear you succeeded.

[CJW2OO4]

How many hours would you say this took?

[F360C]

Originally Posted by CJW2OO4

How many hours would you say this took?

Depends... i would say if your decently mechanically inclined and its your first time doing its probably about 4 hours after the car is on jack stands. I could probably do it in 2.5 now.

[wdb]

Originally Posted by tominizer

Also looks to be some sort of leakage/spray off the driveshaft onto the fuel tanks that I need to look closer at to see where that is coming from........ both sides.

The rearmost driveshaft joint is a constant velocity joint. There is a gasket that is supposed to keep the grease for that joint in place. It doesn't do a great job. I replaced the one on my car, so far so good. My diff input shaft seal was also leaking, seeping is more like it. That did not fling anything around.

[Vanne]

wanna come over and do mine? but when you get here, were just gonna drop the whole subframe, i recon thats way easier that what you did

beers on me

[tominizer]

Vanne Sure. I think there's a flight leaving tonight !!!

Funny though. The thought had occurred to me as I was "balls-deep" into it to just pull it all down (subframe) and clean it all up. Make it good as new and get rid of the years of surface crap as I've done in the past with many other projects. Thing is I also remember that those sorts of actions usually lead to $$$ and me rebuilding stuff that doesn't need to be touched for now other reason than cosmetics/art. Have to stop doing that......... so I can continue to buy food and pay bills