Get the 722.6 Transmission serviced!
 

I think it Aklim who has harped on this before, but to reiterate:

I went over this in the Tech section when it was happening, but I know alot of you have these cars (W210) so I thought I would post it here.

I was having some trans issues so I cracked the sealed dipstick hole and added some fluid, which worked for a week. Then I took it in: There was non-metallic "debris" built up under the shift plate. My guy says it could be broken down fluid, gaskets, who knows, but it wasn't metallic. This gunk was causing too large of a gap under the shift plate and the K-40 relay was getting bad signals on when to shift based on this gap. Anyway, my mech told me that he has seen quite a few of this same situation, and that several have let it go too far and had to replace that $7K shifter. I got a new K40 relay, new shift plate, two seal rings of some sort, and tranny pan gasket, a filter and 9 quarts of fluid for $650 (probably 100 off for cash) and I now have piece of mine. BTW--my E300 now has 98K on it and he recommends the service at or slightly before 100k.

Get the thing serviced--this transmission has a reputation for failure, and one wonders if it is because MB suggests that it is sealed for life.

Sounds like exactly what happened to mine.

I did mine at 60K and the fluid was a little discolored. Going to do it again at 120K and see what it looks like. At 60K it was because it was now my car. Just bought it and wanted the fluids changed. SA said there was no need but I wanted it done. We shall see what it looks like before I make any other comments. There is no procedure so you will have to do a time and materials thing.