Hi everyone,
This is my first post on MBWorld so please spare me if I'm not following any guidelines or have some information incorrect... I just finished replacing the transmission mount on my 2010 C300 4Matic Sport (Canadian) with 170,000KMs and thought I'd make a streamlined DIY guide which is based off the WIS document attached. I've taken some pictures from pelican parts and a W212 DIY post as well (Credits go to the user "socci" | https://mbworld.org/forums/e-class-w...mount-diy.html).

After jacking up your car, these are the steps you will need to perform:

Step 1: Remove the 6 bolts holding the rear engine tray. (Use an 8mm hex socket to remove the bolts, highly recommend using an electric screwdriver/ratchet to help speed up this process.)

Step 2: Remove the 6 bolts holding the transmission tray. Ignore the two yellow arrows. (Also use an 8mm hex socket.)

Step 3: Support the transmission by using a hydraulic/bottle jack and a thick piece of wood with a decent surface area. Do not directly jack up the transmission belly pan with no wood piece as you may puncture or warp the transmission pan. The jack used in this picture is a bottle jack.

Step 4a: Remove the 5 nuts securing the transmission mount to the crossmember. Nuts are all circled individually in red. (Use a 13mm deep socket to remove the nuts. Having an impact gun will help speed up the process.)
Step 4b: Remove the 8 torx bolts (4 on each side) securing the crossmember in place. Area is circled in red. (Use a 3/8" hex socket to remove the bolts. If you have an e-torx socket set, I believe it should be the E13 socket. DO NOT use the E12 or the E14 socket as the heads will strip.)

Step 5a: With the crossmember off, you should see the transmission mount (Left photo). Next, remove the 4 torx bolts (2 on each side) securing the transmission mount to the transmission. Bolts are circled in red (Right photo). (Use a 3/8" hex socket to remove the bolts.)

Step 5b: With the transmission mount removed, the area should look like the photo below. I'd highly recommend taking the time to clean the area around the transmission before reinstalling the new mount.

Step 6: Install the replacement transmission mount by fastening down the 4 torx bolts removed in step 5a. Torque all 4 bolts down to 28NM in a star pattern.
Step 7: Reinstall the crossmember back into place by fastening down all 8 torx bolts (4 on each side) removed in step 4b. Torque all 8 bolts down to 30NM in a star pattern. Once completed, retorque all 8 bolts down to 50NM in a star pattern.
Step 8: Fasten down the 5 nuts removed in step 4a. Torque all 5 nuts down to 28NM in a star pattern. Once completed, remove the hydraulic/bottle jack supporting the transmission.
Step 9: Reinstall the transmission tray by fastening down the 6 bolts as seen in step 2. Next, reinstall the rear engine tray by fastening down the 6 bolts as seen in step 1.

Hope this thread helps for all fellow W204, X204, and W212 owners out there!

Notes:
- WIS document states to remove the 5 nuts in step 4a before supporting the transmission with a jack. I followed the WIS guide in my installation, however, I don't think it matters if you choose to support the transmission prior to removing the 5 nuts. I simply put that step first since I wouldn't need to attach the same photo twice.
- All bolts and nuts were reused and retightened with no issues. I have seen in some threads that users were saying their 4 torx bolts from step 5a were loose after trying to retighten the bolts. I think that may have been caused by the bolts being overtightened in the first place since I had no issues with mine...
- As I am newbie, this job took me a little under 3 hours since I had to find the right socket sizes and took quite a bit of time to clean the transmission mount area and the crossmember. If you have a 4 post lift, or can work pretty fast with no breaks, you can easily get this job done in under an hour.
- The replacement part I purchased was from Rein Automotive (AVT0509) but a Lemforder or Corteco mount will work as well. I honestly don't know if there's a difference as the mount I purchased was also made in the Czech Republic and looks identical to the Corteco mount being sold on FCPEuro. Benz part #'s are 2212400518 or 2042400618.

 

Great in depth post.

I know I appreciate the details and your work providing to others as a reference.

Question , have you done the w204 engine mounts ? I am finding it hard to find good material to refer to when I tackle the job.

 

Hey I haven't done my engine mounts. I've watched many videos but I think unless I have a hoist, it's not something I'd be able to do at home. There's a great tutorial on YouTube but the mechanic is swapping the mounts on a GLK350 4Matic which is essentially the same as the W204. Link is here: