So I understand that MB's current and settled recommendation is to replace the fluid and filter on the 722.6 transmission every 40k miles. However, it occurs to me that this is something of a one-size-fits-all recommendation that doesn't distinguish between trannies that HAVE a torque converter drain plug and those that DO NOT. The difference in the amount of fluid that gets replaced is significant.

So, assuming that MB's blanket recommendation errs on the safe side, would it not be reasonable to argue that, if you do have a TC drain plug, you could safely opt for a somewhat longer interval? My assumption here is that magnet cleaning and filter replacement at 40k is not absolutely critical....that fluid quality and cleanliness are the main issues. But perhaps that assumption is incorrect.

Also, if the main consideration is the fluid itself, why not do a topside extraction once prior to full service?

So, just thinking out loud, I was considering the following regimen on my E300s, both of which have TC drain plugs: fluid renewal via extraction and fill at, say, 50k miles and then full service at 70k miles. Is this a bad idea? If so, why? Perhaps I am underestimating the significance of timely filter replacement.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

It is indeed one size fits all, but i believe it is assuming a TC drain.

I cant remember the exact basic temperature, but I believe it 170
Degrees. For every ten degrees above the base temp that the trans operates at, the fluid life is cut in half. This was on an ASE test many years ago so i dont remember exact numbers, but you get the idea.

If you cruise on the highway with a mix of city driving, the 40k is probably about right. If you stoplight to stoplight a lot, change it more frequently. If you cruise on the highway only, mostly in cool weather change it less frequently. If you tow with it, change it every refuel stop.

As long as youre not really stretching it, you can skip the filter change occasionally as long as youre always keeping fresh fluid.


Hope this helps.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

If so, it's odd they would make such a recommendation knowing full well that many of the trannies (I think 1999 was the transition year) don't have TC drains.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I hope you aren't serious about changing the trans fluid each refuel stop if towing. That would get WAY expensive WAY fast, not to mention the frequency of changes.....722.6 fluid is like $15 a bottle.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

you can remove the same amount of old ATF even if your car does not have the TC drain, Undo the cooler connection, slip a pipe over it, start engine and collect old ATF - 3 litres at a time.

I do that on GM transmissions which dont even have sump drains.

btw the 722.6 does not actually use a filter like the older transmissions had, it only uses a foam strainer. The nice part about this trans is that all ATF is dumped into the pan very easily while it works unlike the older transmissions which trap fluid (and hence wear materials)

the newer ATF 134 is not as stout as the original ATF 3403M115 which was factory filled. Hence its best to change all the approximately 10 qts of ATF in it every 40,000 miles or sooner if working hard

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

I've always suctioned out & replaced the contents of the transmission pan at every oil change. At the recommended interval, I drop the pan and change the filter. My car doesn't have a TC drain plug, so I'd never get more than 1/3 of the fluid with "normal" procedures.