Over the weekend I did the AFT drain/replace on my wife's 2015 C300 4matic that has a 722.961 trans and for the first time I used a CTA 7650 low pressure drain tool that I picked up late last summer. It had been about 45k since the last one done by the dealer. I've been wanting to try this tool out so I was really looking forward to seeing if it really did anything.

This tool uses low pressure air (about 7-8 lbs) pushed into the oil filter inlet to push out ATF from the lines and valve body and on mine it pushed out an additional 2.8 L. The tool is just a low pressure regulator powered by your shop air (I would not do this without some sort of dryer on your shop air but the manual does not discuss that) and an adapter that bolts right into the valve body where the filter would insert into. It took about 20 mins to push out most of that 2.8L, but I let it run a bit more but it was basically done - just very minor drips after 25 mins, and I shut it down after 30 mins. This is a slow push so its not a power flush or anything like that. I think it is too slow for a shop to consider but for DYI, that's not much of an issue. Naturally it does not do anything for the torque converter but you hear a lot of bubbling as the air is pushed through that. The same thing for the transfer case - lots of bubbling sound but it does not push anything through that since the transfer case has an exit port that is intended to be in air.

So for the change I had the following (this was what I measured prior to cleaning everything up the next day).

Pan drop: a tad under 4.4 L
CTA 7650 push: 2.85 L
Torque converter drain: 2L (this exactly matches the WIS)

Total: 9.25L Capacity for this unit is 9.7 L (this does not include the 700mL for the transfer case. It's a total pain to get to the fill I so I did not drain.)

I pushed in 10L (more like 9.75 after my own tipping over a bottle) of Shell ATF 134 FE and at 45C about 150mL came out until it was just slosh drips and at the correct level. As others have reported I took quite some time to get the fluid to 45C - it was cold when I did that (40F or so) and I'm using a MB star C5 as the scan tool - it took about 30 mins of idling. Later the next day when I was cleaning everything up I was able to get another 150mL from the pan, ATF filter, and rags I used so it would be more accurate to say I got just under 9.4L out total, pushed in 9.75 and drained out .15 so it looks like my drain only left about 200mL in the entire system (and the 700mL left in the transfer case) or the unit was a tad low - in any case its close enough so I felt both that the trans was not significantly low and the fill makes sense for correct level.

To push in the fluid I used a new cheepo red hand pump on Amazon - about 10 pumps per liter - and a CTA 7415 adapter connected to a small air valve I picked up at Harbor Freight. It was fast enough for DYI I don't see any reason to have an expensive pressure pusher given how rarely I will do this.

The fluid that came out had a dark color but was still green in tint - no bad/burnt smells - just looked like medium dirty fluid that was still good - about what I expected for 45k miles. Some minor paste in the pan around the magnet - nothing that alarmed me and pan cleanup was easy. I did not bother collecting any to send off for analysis.

Some models have an auxiliary AFT cooler - that is controlled by an thermostat that does not open until 90C(!) so that did not get any fluid pushed out - that fill is in addition and I did not look that up in the WIS since my push would not drain that. I do need to do more research on that feature and how to identify it for completeness. The WIS atf fill instructions makes reference to that unit and you have to get the ATF to over 90C if you drain it (repairs) in order for it to fill back up. It talks about running the car for at 2500rpm in park until you hit that and I have no idea how long that would take.

A note on the transfer case on the 722.961 - it gets its fluid from the aft cooler return line, and runs it through a reducer which only lets 100mL/min flow into it (at operating pressure), and it is designed to drain back to the transmission at 700mL (that is what the WIS says). So if you drain it from the accessible drain plug but don't fill it - it will take 7 mins of running for it to fill itself - who knows how much damage you will do in that time. Since the fill plug requires lowering the trans since it is completely unaccessible otherwise - safer to just leave it alone. (I'm not aware of any adapter for those threads to do a push fill).

On this trans a hint for those that have not done it. The pan bolts need a E10 socket - no big deal. But the passenger side rear most bolt has super low clearance with the trans mount bracket, so you need a 1/4" swivel E10 to make it easy. Saw a note related to this on a post in the benzworld forum so I was prepared - I don't think you could get on/on/proper torqued with a 3/8 E10 socket even with a swivel - there simply not enough room. But the combined 1/4" E10 swivel was no issue. I used VIM tools entire kit UJET400 (it had the E10 in it) from JB tools (Amazon has it also). Remember use new bolts and two stage torque - 4NM followed by 180 degrees.

I took some video of it, I'll add that to this post later once I upload it.

In summer I'll use the kit again on my sons 2003 E320 and daughters 2000 C230K and I'll report if any issues.

Edit - Here is the video: