X166 Lower Control Arm Replacement
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GL550
X166 Lower Control Arm Replacement
I recently had to replace the lower control arms on my 2014 GL 550 and couldn't find any write up on it. Just to help people out, its pretty straight forward once you have all the correct parts. I ordered control arms and ball joints from Eeuroparts. The Bison brand ball joints were sent to me in error and they did not come with a replacement nut for the bottom of the ball joint and the nut that I removed did not fit, so they were useless. I would stay away from those. I ordered a TRQ from amazon and it came with its own nut. I also ordered a Dorman brand and that fit with the original nut. The Bison and the Lemfoerder brand control arms seemed to be of equal quality, but can't make any assessment of long term reliability. The original ball joints actually seemed pretty good and probably didn't need to be replaced, but since it was simple to do I just went ahead and replaced them. I will also note that the local MB dealer wanted $200+ for the OEM ball joint and $750 for the control arms, so I highly recommend looking online to save a ton of money.
Before you start there are several special tools that you will need to complete this: 46mm socket (and likely a 1/2 to 3/4 adapter), 46mm wrench (a 48mm 12 point wrench in a kit at Harbor Freight also worked), 24mm wrench, T45 torx bit, 16mm hex socket, and 22mm socket.
1) Jack the car up. I did both sides, so I used the front jack point under the front, center of the car and then put a scissors jack under one side and a jack stand under the other. I also had a spare scissor stand that I used to help get the control arms in place.
2) Remove the wheels.
3) Remove the shields. There are lots of write ups on this. My car has the off-road package, so it can be very difficult to get off. You may want to have replacement bolts/nut if you haven't removed the shields before.
4) Since I knew I was replacing the ball joints, I loosened the bottom nut first, since you have to have a lot of leverage (Skip this step if you are not replacing the ball joints). You need a 46mm socket to fit the bottom. I also needed 1/2 female to 3/4 male adapter so I could use my 1/2 breaker bar. They nut is on so tight I also had to use the top half of my floor jack on the end of the breaker bar in order to get enough leverage to bust it free. Once you loosen it, the ball joint will spin freely so you cannot use the socket to remove it, so you actually need a 16mm hex socket and I used a 48mm wrench that came in a kit from Harbor Freight. You could also special order a 46mm wrench online.
5) There are 3 connection points for the control (other than the ball joint). There is one bolt where the front shock attaches near the hub/knuckle. It is a 22mm bolt on one side and the other side is fit into a slot so that it does not rotate when you loosen/tighten the nut. However, in order to remove the bolt towards the front of the vehicle, you have to remove the bolt connecting the torsion bar to the end link. This is an 18mm bolt.
6) The front connection point is a single bolt. It is a 21mm bolt and a 21mm nut. This is straight forward to remove, you just need a breaker bar. However, in order to get the bolt out, I had to undo the 2 bolts mounting the torsion bar to frame of the car. I have Active Stability Control, so I don't know if the install points are the same for the traditional torsion bar. The bolts holding the torsion bar are also 18mm on my vehicle.
7) The rear connection point has 2 short bolts. The first is horizontal and has 21mm bolt and a 19mm nut. The vertical bolt is a 21mm with a 21mm nut on top of the frame support. I had to bend a heat shield up in order to access the nut on the passenger side. I loosened the bolt from the underside first using the breaker bar and then was able to get it to come out.
8a) If you are not replacing the ball joint, once you get the 4 bolts removed, you need to maneuver the control arm so that you can get the 24mm box end wrench onto the top nut of the ball joint. You then need to get the T45 torx into the top shaft of the ball joint to stop it from spinning. I used a really long 3/8" extension to get it past the side of the knuckle to keep it from spinning and then muscle the nut loose.
8b) If you are replacing the ball joint, drop the control arm down and then lift the ball joint out of its seat to remove the entire control arm. You do not need any special tools to get the ball joint unseated.
Congrats, you have the control arm removed and are ready to reinstall.
9) If you are replacing the ball joint, I installed the new ball joint into the control arm so you can get it tight very easily.
10a) If not replacing the ball joint, first insert the control arm at the ball joint by sliding the ball joint bolt through he howl of the control arm.
10b) Install the new control by getting the ball joint seated into the knuckle first. It is a little tricky to get the control arm back into place to get all the bolts through. I used a spare scissor stand in order get the front mount into location and then hammered the rear mounting point in place. You also need to make sure you get the control arm slotted in between the lower mount of the shock. One by one I would get the bolts into the appropriate holes - usually it takes a little hammering to get the holes lined up...they are tight tolerances.
11) I first tightened the rear two bolts. Then moved to the front bolt. Then re-install the bolts holding the torsion bar to the frame. Reinstall the bolt through the control arm at the shock - don't forget the bolt at the shock has to be inserted from the front of the vehicle and properly lined up in order to go all the way through. Once all the 4 bolts are tight, I then jacked up the knuckle in order to align the torsion bar and the end link. Once you get the end link secured, lower it back down. If you replaced the ball joint, now is when I replaced the bottom nut back on the ball joint. Again, you can tighten it to a certain point using the socket, but in order to tighten down you need to use the 16mm hex nut and the 46mm/48mm wrench to get it tightened down.
12) Reinstall the shields.
13) Reinstall the tires.
14) Lower the car back down.
Overall, this is a relatively straight forward job and I spent about $600 for 2 control arms, 2 ball joints, a socket set with 24mm wrench, a socket set with 48mm wrench, 16mm hex, and 46mm socket and adapter. The dealership charge was $3,000 ($1,500 parts and $1,500 labor) and did not include replacement of the ball joints. Total job time from start to finish was about 4-5 hours once I had all the correct parts...which includes getting all the parts, jacking up the car doing the work, and clean up.
Before you start there are several special tools that you will need to complete this: 46mm socket (and likely a 1/2 to 3/4 adapter), 46mm wrench (a 48mm 12 point wrench in a kit at Harbor Freight also worked), 24mm wrench, T45 torx bit, 16mm hex socket, and 22mm socket.
1) Jack the car up. I did both sides, so I used the front jack point under the front, center of the car and then put a scissors jack under one side and a jack stand under the other. I also had a spare scissor stand that I used to help get the control arms in place.
2) Remove the wheels.
3) Remove the shields. There are lots of write ups on this. My car has the off-road package, so it can be very difficult to get off. You may want to have replacement bolts/nut if you haven't removed the shields before.
4) Since I knew I was replacing the ball joints, I loosened the bottom nut first, since you have to have a lot of leverage (Skip this step if you are not replacing the ball joints). You need a 46mm socket to fit the bottom. I also needed 1/2 female to 3/4 male adapter so I could use my 1/2 breaker bar. They nut is on so tight I also had to use the top half of my floor jack on the end of the breaker bar in order to get enough leverage to bust it free. Once you loosen it, the ball joint will spin freely so you cannot use the socket to remove it, so you actually need a 16mm hex socket and I used a 48mm wrench that came in a kit from Harbor Freight. You could also special order a 46mm wrench online.
5) There are 3 connection points for the control (other than the ball joint). There is one bolt where the front shock attaches near the hub/knuckle. It is a 22mm bolt on one side and the other side is fit into a slot so that it does not rotate when you loosen/tighten the nut. However, in order to remove the bolt towards the front of the vehicle, you have to remove the bolt connecting the torsion bar to the end link. This is an 18mm bolt.
6) The front connection point is a single bolt. It is a 21mm bolt and a 21mm nut. This is straight forward to remove, you just need a breaker bar. However, in order to get the bolt out, I had to undo the 2 bolts mounting the torsion bar to frame of the car. I have Active Stability Control, so I don't know if the install points are the same for the traditional torsion bar. The bolts holding the torsion bar are also 18mm on my vehicle.
7) The rear connection point has 2 short bolts. The first is horizontal and has 21mm bolt and a 19mm nut. The vertical bolt is a 21mm with a 21mm nut on top of the frame support. I had to bend a heat shield up in order to access the nut on the passenger side. I loosened the bolt from the underside first using the breaker bar and then was able to get it to come out.
8a) If you are not replacing the ball joint, once you get the 4 bolts removed, you need to maneuver the control arm so that you can get the 24mm box end wrench onto the top nut of the ball joint. You then need to get the T45 torx into the top shaft of the ball joint to stop it from spinning. I used a really long 3/8" extension to get it past the side of the knuckle to keep it from spinning and then muscle the nut loose.
8b) If you are replacing the ball joint, drop the control arm down and then lift the ball joint out of its seat to remove the entire control arm. You do not need any special tools to get the ball joint unseated.
Congrats, you have the control arm removed and are ready to reinstall.
9) If you are replacing the ball joint, I installed the new ball joint into the control arm so you can get it tight very easily.
10a) If not replacing the ball joint, first insert the control arm at the ball joint by sliding the ball joint bolt through he howl of the control arm.
10b) Install the new control by getting the ball joint seated into the knuckle first. It is a little tricky to get the control arm back into place to get all the bolts through. I used a spare scissor stand in order get the front mount into location and then hammered the rear mounting point in place. You also need to make sure you get the control arm slotted in between the lower mount of the shock. One by one I would get the bolts into the appropriate holes - usually it takes a little hammering to get the holes lined up...they are tight tolerances.
11) I first tightened the rear two bolts. Then moved to the front bolt. Then re-install the bolts holding the torsion bar to the frame. Reinstall the bolt through the control arm at the shock - don't forget the bolt at the shock has to be inserted from the front of the vehicle and properly lined up in order to go all the way through. Once all the 4 bolts are tight, I then jacked up the knuckle in order to align the torsion bar and the end link. Once you get the end link secured, lower it back down. If you replaced the ball joint, now is when I replaced the bottom nut back on the ball joint. Again, you can tighten it to a certain point using the socket, but in order to tighten down you need to use the 16mm hex nut and the 46mm/48mm wrench to get it tightened down.
12) Reinstall the shields.
13) Reinstall the tires.
14) Lower the car back down.
Overall, this is a relatively straight forward job and I spent about $600 for 2 control arms, 2 ball joints, a socket set with 24mm wrench, a socket set with 48mm wrench, 16mm hex, and 46mm socket and adapter. The dealership charge was $3,000 ($1,500 parts and $1,500 labor) and did not include replacement of the ball joints. Total job time from start to finish was about 4-5 hours once I had all the correct parts...which includes getting all the parts, jacking up the car doing the work, and clean up.
