E55 Transmission fluid change VS Flush
I just do fluid pan changes more frequently and my filter is new. I have lower mileage though. Also replace the electrical connector to the TCU.
If you don't want to go through the hassle of the full change, just do a few partial changes (ie. drain and refill) over the next year or so.
Just to clarify the previous post, you'll want to replace the connector at the valve body/conductor plate, not the connector directly at the TCU (the TCU is under the passenger side carpet). Most dealer parts personnel will probably know of it as a "pilot bushing" (that's what Mercedes calls it, not sure why...).
BTW - You all are great and so very knowledgeable, I know generally what I should do but not all the details.

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Check each distributor in your state as it only lists headquarters and each distributor may have multiple locations.
P2561 THE GEAR IS IMPLAUSIBLE OR THE TRANSMISSION IS SLIPPING 2.GEAR
I would check the TCU under the carpet in the foot well, it is on the left side of my car (RHD). It could be fluid has indeed gone into the unit (it wicks up the wiring), or it could be transmission fluid level (easily checked), or conductor plate (~$200 and a messy DIY in a very clean kind of way) or the possibility which makes you not want this is worn friction plates in your clutch pack which means transmission rebuild.
I think mercedes revised this half a dozen times. Original ones have clear o-rings from memory.
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Check each distributor in your state as it only lists headquarters and each distributor may have multiple locations.
Sorry again. I am learning every day.
Yup... The dreaded 'implausible ratios' code among others.
I took a deep breath and..... Changed fluid and filter.
All issues resolved with fresh fluid and filter.
I drain and fill my five speed boxes every other engine oil change. Fluid is cheap and they always shift better with fresh fluid.
with nothing more than pan drop and filter change (OEM filter and Shell ATF134)
no need for full flush.. my wifes old E320 had 343K when we sold it and trans was still fine. we sold due to SBC problems.
Cheers




Drain the transmission from the plug. Add 4-5 quarts and drive.
5k miles later do a filter swap. add 4-5 quarts.
from this point the fluid should start to have a nice pink color.
Keep up with changing the fluid semi periodically for a strong healthy future.
my 2 cents, Gator





On an E55, remove the air filters/TB intake assembly. You'll find the transmission fill tube in back of the engine and below the throttle body towards the passenger side. Do NOT use the tube in front of the throttle body and visible with air filters installed. The transmission filler tube is behind the engine and below the throttle body.




Fresh gear oil for the differential.
Fresh brake fluid.
Change oil in supercharger.
They are a fantastic car.... Drive it more!
He posts on this site usually in the Tech section.
parts list for 2012 S550 transmission fluid/filter change












