Hello I have a 2009 c300 and havent done any transmission service since the car was bought. I am current at 109k miles and its still running, it seems that its sluggish. So the question is should I flush my transmission fluid or change it? Ive heard that flushing a transmission that hasnt been changed can make it faulty and problems will occur. Any thoughts?

 

An indy MB tech that I trust says don't flush. Drain transmission and TC and change filter. Refill.

 

Most MB dealers don't properly flush either.

 

MB dealers should follow the WIS. In the WIS there is no mention for a "flush", just a drain and fill

 

I don't think I ever heard a reputable source recommend a flush on any AT. Drain Fill & Swap Filter

 

What would you recommend when you have no drain plug on the TC?

 

Me personally - not worry about it

If it was a car I was trying to meticulously maintain, I'd drain & fill the ATF every 30k or so.

 

What I do on the 2001 e430(no TC plug) is drain and refill the pan. After about 1K, I drain again. This time dropping the pan and changing the filter. Refill measuring with dipstick @ 80 C.(both times). I think this gets most of the old fluid changed.

 

Drain and fill a few times. NOT a flush. Those are two separate things.

 

The 722.9 transmission TC should have a separate drain plug, usually have to rotate the TC for access. Should take 2L, plus the approx. 7L for the drive section. Here's the Sticky:

https://mbworld.org/forums/c-class-w...ce-thread.html

 

Can confirm it's around 2L. Just had mine done. Cheers!