This is a tutorial for the process of replacing the rear shocks on an X166 model 2013 GL550. I'm pretty sure it would apply to the similar year GLs up to 2015 (possibly 2016) and 350 and 450 sub-models. The process took me about 4 1/2 hours since I was careful and had no guide to refer to. There are a total of 22 steps, which can take between 4 to 5 hours. Here are the parts and tools I used:

Part(s): 2 x rear ADS and Airmatic shocks P/N A 166 320 09 30 (these are designed for Adaptive Damping System equipped GL550s and possibly the GL63AMG)



Tools: 18mm deep socket (for wheel bolts), 24mm deep socket (for lower shock bolt), 24mm wrench (for lower shock nut), 1/4" and 1/2" torx set, 1/4" ratchet, 1/2" ratchet, 13mm 1/2" deep socket, 1/2" extension (4" long), small flat-tipped screwdriver, and several plastic body panel removal tools.

Step 1: Begin by removing the 4 metal tie-down brackets at the very rear of the storage area of the GL (use flat-tipped screwdriver to remove plastic cover, then 1/2" ratchet with appropriate torx bit to remove bolt):



Step 2: After you pry out the rear side panel covers with your plastic body panel removal tools, you'll see two small black screws. Remove small black screw from lower side body panels using 1/4" ratchet and torx bit:



Step 3: Remove both torx bolts from rear panel (aluminum scuff plates are a part of the panel) and remove panel:



Step 4: Next, remove the two carpet covered flaps that cover the gap between the 3rd row seats and the back floor area. They will require a little pressure to pop them out. Once out, you'll see the 4 silver torx bolts that hold the rear access floor panel to the body via its hinges. Remove those bolts and the rear access floor panel can easily be taken out. Now you should have nothing in the way of the side interior plastic panels.

Step 5: Remove plastic covers for rear and front storage cover retractable shade using small flat-tipped screwdriver, then remove bolts on driver's and passenger's side panels using torx bit:





Step 6: Remove second row seat belt (driver's side and passenger's side) bolts using 1/2" ratchet and torx bit:


Step 7: Gently pull side interior panels out and away from body. The white clips holding them will pop out with just enough pressure. Make sure they stay attached to the plastic interior panel so you can re-install the panels later. Also, you will have to remove the wiring harness attachments with the small flat-tipped screwdriver from the back of the panels that connect the 3rd row seat fold controls as well as the 12volt plug and rear compartment light:


Step 8: Remove the nuts holding the control modules to the side of the rear body using a 13mm deep socket and 1/2" ratchet. These also hold the foam to the interior body. Use the flat-tipped screwdriver and pop the black wire holders off the body screws. There are several modules and wires on each side of the rear that hold down the foam you need to move later to access the top shock mount nuts:





Step 9: Pull back the foam, and using a flashlight, you'll see the two nuts holding the top of the shock to the body mount. Remove both nuts with a 13mm deep socket, 1/2" ratchet and long extension:



Step 10: Jack up the vehicle using the rubber jack areas underneath the rear rocker panels on each side of the vehicle, then remove the wheels using the 18mm deep socket and an air impact driver.

Step 11: Remove the clips holding the rear shock wiring harness using the small flat-tipped screwdriver. You'll need to pull the light gray tab out, then press down on the black tab while pulling the upper wiring harness out. Once you've done that, you can reach under the lower harness that is still attached and push the tab away as you pull down. That will free the lower wiring harness that goes to the shock. It's tricky, but can be done if you have patience. Be careful not to pull the upper and lower harness apart too hard:


Step 12: Using the air impact driver, a 24mm deep socket, and the 24mm wrench, remove the lower shock nut and bolt:



Step 13: Slowly remove the old shock by pulling the bottom out, then guiding the top down and away from under the plastic wheel well splash panel. Since you removed the top mount nuts already, it will easily come out:

Step 14: Inspect and then install the new shock exactly as you removed it. Place the lower mounting bolt through the control arm bushing and hand tighten the nut for now. Allow the top portion of the shock to rest against the plastic wheel lining. Using another jack, begin to lift the control arm assembly from the outer edge near the ball joint while guiding the upper portion of the shock so the two mounting bolts go through the holes at the top of the shock mounting point on the body. You may need to move the top of the shock laterally and spin it to align the holes and bolts. Go slow so you don't pinch yourself, and also so you don't unintentionally compress the shock. It will take patience, but you'll know you have it when the shock sits upright with minimal play at the top.



Step 15: Go inside the vehicle and hand tighten the top shock mounting nuts. Then slowly lower the second jack until the rear control arm is fully lowered. Attach the new shock's lower wiring harness to the plastic control arm panel. Then carefully insert the upper wiring harness into the lower, clipping the light gray tab back in place to lock them together. Then you can tighten the lower shock mount bolt and nut to 180ft-lbs (245Nm).

Step 16: Repeat steps 9 through 15 for the other side of the vehicle.

Step 17: Re-install the wheels, torquing the wheel bolts to 110ft-lbs (149Nm) in an alternating pattern, and then lower the vehicle completely to the ground.

Step 18: Now, go back to the shock top mounting nuts and tighten each to 38ft-lbs (52Nm) for both sides.

Step 19: Place the foam back over the body mounting bolts, re-install the control modules and brackets, and press the wiring harness black tabs back in place over the body mounting bolts.

Step 20: Re-install the plastic side interior panels, carefully maneuvering them into place between the foam and 3rd row seats. Once you have them in place, re-attach the wiring harness clips that you removed for the 3rd row folding buttons, 12volt plug, and rear side light in the back of the plastic interior panel. Be sure to fish the 3rd row seat belts outside of the panels before clipping them back in. Then you can carefully align the panels and press them back into place allowing the clips to lock into their holes on the body. You'll need to use your body panel removal tool to fish the rubber window and rear hatch weatherstripping back on top of the plastic portions since it will be pinched when you re-install the interior panels.

Step 21: Now, you can re-install and tighten the 2nd row seat belt bolts, replace the small black torx screws at the very back, re-install the rear floor compartment panel, re-install the 3rd row seat floor gap covers, and re-install the 4 floor tie-down rings. Lastly, pop in the side access panels, re-install the aluminum topped rear panel and replace its two silver torx screws.

Step 22: Now that you have everything re-installed. Start the vehicle, test all the 3rd row seat switches, test the 12volt socket, ensure the vehicle is level, and test the Sport/Comfort mode settings using your button on the center console. Then go for a 15 minute test drive and ensure the vehicle rides smoothly without any thuds, creaks, or notifications on the instrument panel. If it was like my test drive, you'll immediately notice a smoother ride over bumps and no more side to side hop over ruts and large bumps.

I hope this tutorial was helpful. I appologize for omitting the torx sizes since I did not have markings on my set for reference. If I am missing any details, please let me know, and I'll update the post to reflect the corrected info. Good luck on your future Mercedes GL repairs. Taking on this repair can save you $1500 over most dealer quotes. My next task will be tackling a check-valve install and replacing the timing chain tensioners on my M278 equipped GL with a rattle timing chain upon startup. I'll post a detailed tutorial once I am finished with that repair.

 

NICE write up!

 

I have the sport/comfort button on my GL350 but not the off road dial. I have a few questions:

When you say ADS do you mean the sport/comfort option (standard on 550) or the off road dial option?
What were your symptoms? Was it just rocking after bumps? No leaking sounds?
How many miles are on your vehicle/struts?

 

Thanks, Landon!

 

ADS is actually the type of shocks. ADS equipped vehicles have shocks that can automatically adjust their viscous damping continuously while the vehicle travels, and can adapt to constantly changing road conditions. Airmatic is the system that includes the Sport/Comfort setting, and changes the ride type from soft to sporty based on adjusting pressure in the airbags. The Off Road option on GLs adjusts the ride height to clear under vehicle obstacles while also locking the differentials and comes with skid plates.

Here is a link to a site I found that explains the ADS and Airmatic systems in more detail: www.loebermotors.com/blog/what-is-a-mercedes-benz-airmatic-suspension/

 

Just got quoted $2,844.74 with labor and parts. Or $1,000 with just labor and I bring own parts.

This is for both rear shocks with ADS.

 

That's about what my dealer quoted me too. You could probably find a cheaper option with an indy shop, but doing it yourself will cost about $1100 in my experience.

 

Anyone try these? https://www.ebay.com/itm/Pair-For-Me...tY7dr5&vxp=mtr

I ordered OEM parts, I don't know if I trust those. One of mine started leaking at 58k miles so doing both at the same time.

 

I just ordered two from https://www.genuinemercedesparts.com...omponents-scat.

Was $1,117.16 after tax and shipping.

I am going to take it to my local independent shop for install. Loeber Mercedes wanted $800 plus for install. They also wanted around $2000 for the parts. (Crazy)

I'm guessing my independent shop will charge around $500-600 for install.

So I should be out a total of $1700 ish.

 

in step number 9, where you jack up the car, did you use jack stands afterwards or did you leave the truck on jacks? If you did use jack stands, where did you put them? Thanks.

 

excellent write up! I just did mine..pretty easy job.

I would recommend jacking the car up, and putting it up on a stand on the corner that you are working with... take the tire off then use the jack under the hub to move it up and down as once you unscrew the screws at the top of the shock.. the whole assembly will plop down! You need to be able to move the assembly up and down to remove and reinstall the shock.

Also, I would highly recommend doing both rear shocks as it really transforms the car back to "new feeling" spec.

 

Maneesh,

I used a 3 ton low profile quick jack on the rubber lift point in front of each rear tire, and behind each front tire. After I jacked up the rear on one side, I put a 3 1/2 ton jack stand under the pivot point of the lower control arms; ensuring it was locked and secure under the vehicle. I then repeated the step for the other side. Once both jack stands were securely placed under the vehicle, I then put the jack under the back hitch receiver area and jacked it up just enough to put slight pressure on the hitch. That way it would catch the vehicle if the jack stands slipped. However, this repair is rather safe because it doesn't require you to be under the vehicle much at all. Good luck!

 

Cyclrder,

I did both of my rear shocks as well, and would highly recommend it since one leaking means the other is likely to follow suit soon after. Next up, I'll be replacing the front air struts with some Arnott remanufactured struts as well as replacing the weakened joints in the suspension system up front. I'll definitely do another write-up for that process.

 

NolaGL550 - First, awesome job on the tutorial. I replaced both shocks over the weekend and it was much easier working from your notes and pictures.

One question I had was whether to tighten the lower shock bolts while the suspension is hanging down (vehicle still jacked up) or whether it would be better to lift the suspension to it's "normal" position before tightening? I wasn't sure if you were working from a manual or not. When I replaced suspension bushings on my Audi, the factory manual specifically said to put the suspension in its "at rest" position before tightening various bolts.

 

Generally, the wheels (weight of the car) should be on the ground before torquing the lower shock bolt fully.

 

 

 

 

Here are the torque specs for the rear shocks...thought this might come in handy if you are performing the repair (see the Model 166 portion for 2013+ GLs):

 

 

That's nuts that it's not covered under the EW, I was thinking about getting an EW to cover this very thing for the future, now I'm having second thoughts. Please do keep us posted on what MB USA replies back.

Best of luck, hopefully they made a mistake and you're covered.

 

 

I'm in a similar situation, debating if I should find a 3rd part extended warranty. However, in my research I've found that most warranties while they cover suspension, they exclude struts/shocks. Even the top of the line exclusionary warranties exclude these parts. Has anyone found a reliable 3rd party warranty that will include them?

 

The ELW is still very valuable for the price you pay. I would 100% get it if it was available for my MB.

 

I agree, but unfortunately the ELW is only available to cars that are still under factory warranty. Unfortunately, I bought the car after the original warranty expired. Do you recommend any 3rd party warranty providers?