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Lower Control Arm Replacement (LCA)

11K views 2 replies 3 participants last post by  Rittmeister  
#1 ·
When I researched this job, I couldn't find any dedicated DIYs on it, so I figured I'd give a quick write-up to help give people some confidence to tackle it. To be clear, this is for the lower control arms, or LCA, not the "thrust arms" that more commonly fail.

To start, jack up the front, support on jack stands and remove the front wheels. I started by spraying the ball joint connections, and other nuts with a liberal amount of PB Blaster to help with removal. I also recommend replacing the front sway bar links when doing this job because they only cost about $50 for both and it adds less than 30 min to the job.

Step one is to remove the bolt connection on the frame with a 5/8" socket on one side and 18mm wrench on the other side. On the passenger side you'll need to unclip the headlight leveler, I think this popped off with a screwdriver. This bolt comes out pretty easily (unlike the similar bolt on the thrust arms)

Step two is to loosen the 22mm nut on the ball joint side. This takes a little while due to the lack of space, but you don't want to take it all the way off. Leave it flush with the top as shown in the picture.

Last removal step is the hardest part. I bought a 12" pickle fork from harbor freight to remove the ball joint connection, but needed to grind about 1/4"-1/2" off the tip. Without modifying the fork, you'll hit the brake shield before popping the joint. If you have any type of bench grinder it makes short work of the soft metal. I was finally able to use my cheapo craftsman grinder that has been collecting dust in my basement for 3 years.

I aligned the pickle fork as shown in the picture, and went after it with a 4 lb hammer. The night I started on it, I was unsuccessful, quickly gave up for the night, but the next morning they gave way after about 12 wacks.

At this point I also removed the sway bar links with the same 5/8" socket and a 17mm open wrench to hold the ball joint, and installed the new links.

Installing the control arms is pretty straight forward. I got the ball joint started in the collar while lining up the opposite end to secure the bolt/nut. I left the bolt loose for the time being. One you get the ball joint 22mm nut threaded down a bit, the joint will start to spin with the nut and you'll get nowhere. To counter this, I placed my jack (with hockey puck pad) under the ball joint to apply pressure. With the jack in place, you can torque the nut down. I wasn't sure if this next step was necessary, but before torquing the bolt on the frame side, I leveled the suspension, similar to what is needed for a thrust arm install.
 

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#2 · (Edited)
Thanks for the write up, great work. I just did this job too in the summer. I bought a car that had a shot drivers side LCA. The ball joint had ÂĽ" of slop and the rubber bushing was coming apart on the other end. I think as these cars age we'll see more of these LCA'a fail. I too looked for a DIY and didn't find one back in the summer. The steering had a mind of it's own with this shot wishbone.

As you say the biggest task is getting the ball joint separated. The post on the ball joint is unusually long so most generic ball joint "scissor type" separators don't have the reach to pop it out. Luckily I know someone that works at a BMW dealer. He let me borrow his BMW ball joint tool. That made the job much easier.

And yes you want to set the wheel at normal ride height (pre load) before tightening the wishbone to frame bolt. I read some BMW spec that says to load the car with around 500lbs of weight distributed evenly in the passenger cabin (125lbs in each seat etc) to set the pre load. I just did mine using the weight of the car. I measured the distance from the lip of the fender to the wheel center with another car on the ground, set it there and tightened it with the car with the wheels on old railroad ties I had laying around.

If you have some short ended allen wrenches I think they may be able to hold the ball joint post from turning by holding the allen socket in the ball joint. I can't remember how I did it now, but remember thinking I need some stubby allen wrenches like this:

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This is the ball joint tool:

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