Hello everybody! As I mentioned in my main thread about my C55, I am 7-speed swapping my C55 with a 722.9. I said I would show what I did so this is that thread. Hopefully this helps some people, or maybe pushes others to do it if they didn’t want to go the manual swap route but still wanted something different than the 722.6. This isnt a perfect guide, this is more to show what I did, as some parts of this can be different depending on the exact model of 722.9 you use.

Why the 7-speed? Long story short, I’ve seen it done before and wanted to do it since before I even owned a C55. I originally planned to manual swap the car, but a friend who also did this showed me how straightforward this swap really is. I also found this transmission for a great deal and a few years ago I was basically told, “Pay us to do it or don’t bother,” by a company doing these swaps. That honestly made me want to do it myself and share the information even more. I’m not 100% finished yet, but I’m very close. It should be done within the next month or so. I’ll continue updating this thread as I go — especially once it’s fully complete.
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What I’ve Done So Far Transmission The first thing I bought was the transmission. Many 722.9xx variants will work. The specific unit I used was a direct bolt-in. All bellhousing bolts lined up and it bolted directly to the M113 with no modification required.

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Flexplate I sourced the flexplate from an M156 car (purchased on eBay), although this flexplate is shared across many models. It bolted directly to my M113 with no issues.

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Transmission Cooler Lines These need to come from an M113 + 7G-Tronic CLK500 (2005–2006 in the US). Part numbers: A209-270-48-96 A209-270-47-96 These route correctly and connect properly to the 722.9 and original radiator.

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Driveshaft This also needs to come from an M113 + 722.9 CLK500. It is slightly shorter and uses a 3-bolt flange. If your transmission has the 4-bolt output flange, you will need to swap it to a 3-bolt flange (I had to do this on mine).
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Shift Linkage I used the shift linkage from an M113 + 722.9 CLK500.


I forgot to take a pic of mine LOL

--- Mount / Crossmember I retained the OEM crossmember and installed a new OEM transmission mount. Everything bolted together directly. I just had to move the crossmember back one position and tap the existing holes in the chassis to accept the OEM bolts.
This pic shows well the extra holes, these are there for different engine/transmission options these came with, i had to go one further back (to the right on this image)

--- VGS (722.9 TCU) The VGS is the transmission control unit and conductor plate for the 722.9. Unlike the 722.6, which uses a separate TCU mounted elsewhere in the car, the 722.9 integrates the control module into the transmission. This will need to be reprogrammed to work with your vehicle. It is VIN-locked, and certain parameters (such as gear ratios) must match your setup.

VGS and valve body connected.

--- Wiring / Electronics This part is much simpler than most people think. It’s essentially 4–5 wires: Power Ground CAN High CAN Low (Sometimes K-line) I removed the old 722.6 TCU and associated wiring and connected these accordingly. That’s it.

Before i wrapped the new harness

--- Like I said, I’m not completely finished yet, but I’m extremely close. I’m really looking forward to having this done. The faster shifts, tighter gear ratios, and improved overdrive make this an upgrade over the 722.6 in almost every way. I really think the car will be much much more enjoyable. Ive driven quite a few 7 speed cars and owned/own them, i love the 7 speed much much much more. I’ll update this thread once everything is 100% complete and will share videos of the first drive and overall results. For now, I was excited and wanted to start documenting it and getting the information out there.

 

Nice write up. This is interesting and I’ll be watching.

 

Nice write up
The stock shift linkage fits the 7G, since you can adjust it

 

Very impressive! Even though I sold my C55 many years ago, I look forward to seeing the results of this!

 

Cant wait till done. As you know frominstagram, I am doing the same swap. My transmission is already in the car, waiting for a few more things before car is drivable.

 

All the C55 with 7G swaps are waiting in the pipeline to fire up hahaha

 

I'm very curious about the subject. Such transformations are not made much, even if they are made, they are kept as a state secret. I hope the transplant is successful and how to do it will be explained in detail here.

 

Hello everybody, i am glad to see alot of people replying to this

Big news!

I got the vgs, key, ecu, eis back from the mercedes swap shop today. I plugged it all in, and its working great! Dash shows all 7 gears, xentry scanned, cleared codes, range select is working, its all working great! I need to finish up a few small things on other parts of the car, but first test drive coming very soon!

 

a video was just dropped
maybe it is one of the posters here

 

I literally just came to send this here!!!! Haha yes this is one of the posters here, he has also made his own thread with the video i see, great video!

 

Thanks guys. Yo I didnt wanna hijack your thread so I started my own. Either way, its a team effort at this point lol

 

Hello everybody, finally got out on the road.
i can definitely say i am very very pleased with the swap, sooo good.

If you wanna see a quick acceleration run with the .9 swap, here ya go!

 

Same, my car is also done. Its a different car for sure.