I did mine the other week with the pump I listed and it was a great pump, process wasn't too bad but long. These videos were helpful with the torque converter, but I'll admit I did it on the c63 (rwd) and not the c300 (4matic) yet.

 

Im wondering if people blow out the transmission to try and push all the old fluid out. I did have the CTA adapter kit but ended up returning it, even though i got it cheap I couldnt justify spending $80 just to use it once. Instead I was thinking of making my own adapter out of pvc, went to Lowes and was messing around with the fittings and think i have a good idea.


The adapter is a little wider than the tube on the trans filter. Probably because it doesnt fit up in there as high.






I measured with my cheap calipers to try and find something with the same diameter. But realized good luck.



Forget what size this is, maybe 3/4". Its wider than the tube, so will fit flush on the transmission where the filter fits in. The other side is threaded to receive a cap.



Cap threaded on. Then just drill out a hole to fit on a 1/4 quick connect. I can either thread it with my tap set or simply epoxy it in.

For a seal just stick on some foam weather stripping. Connect the air hose then have to hold it up over the hole while the compressed air hopefully pushes all the trans fluid out. Wonder if its worth doing. PVC parts are only $4. I saw a video and the guy says he got an extra 2 liters buy pushing the fluid out with the cta adapter.

 

I would strongly advise against pushing fluid through the transmission. You run the risk of dislodging and forcing solids through the small fluid passages and causing problems. There are many horror stories on the web.

 

I wouldnt be pushing new fluid through, just air from the air compressor. I also bought an oil/water filter to plug in line on the air compressor line to make sure no water is being blown in. I was thinking low pressure, 5-7psi. isnt the transmission fluid pressurized through the transmission anyways? I tried to search real quick for what typical transmission fluid pressures are and seems they are well over 7psi. Unless im totally wrong. Im in no way talking about blasting air in, just a gentle push. It would be so low that im thinking id have to hold it up there awhile, was thinking of ways to have it held up there so my arm doesnt fall off. Before I returned that cta kit I matched up the bolt they use to screw the adapter to the transmission, can devise a way to screw it down.

Your comment about dislodging things does make sense so i did some quick searches and found this article interesting and also makes sense to me:

-------------------"In almost every case, when a vehicle owner states that his or her transmission failed shortly after a flush was performed the flush was done using a high-pressure flush machine at a repair facility. Here’s why:

A transmission flush machine uses high pressure along with a cleaning agent to flush the old fluid out of the transmission while simultaneously cleaning the internal parts. During this process, the high-pressure cleaning does such a thorough job that it dislodges dirt and debris that the transmission’s internal pump is not strong enough to do.

If, while being flushed through the transmission, a piece of debris becomes lodged in a more crucial are of the transmission it can cause problems, even catastrophic transmission failure. High-pressure flushing machines can also blow out internal seals in high-mileage transmissions."
-------------------

From the records i have on my vehicle the transmission was "serviced" by Mercedes Benz of Portsmouth at 43,000 miles and then again by Dreher Holloway Mercedes Benz at 79,000 miles. I have no idea what "service transmission" includes but im thinking at least the fluid and filter was changed. I will say the vehicle does appear to have been well maintained, when I did the front and rear differential fluid I was surprised to see the fluid looked really good like it was recently changed. I dont even see records for that work.

So, i wont be using high pressure and i wont be using a cleaner. Do you think I still may run into an issue?

 

Id say it still isn't worth the risk. Considering its already been done twice that's more than 80% of these cars get from their owners.

 

What initially made me want to do the fluid and filter was it recently hit 150,000 miles and theres quite a list of things to address in the maintenance manual. Then I saw the condition of the pan, rusted and bubbling and now im paranoid of it failing. I figure once the colder weather starts rolling in I wont want to work on it at all, so nows the time to do it, or wait until next spring and hope nothing goes wrong.

 

Drain the fluid, drain the torque converter, and replace the rusty pan. Then, you're in good shape for the winter and the next 50,000 miles.