This is a longshot, but thought I'd try here since it seems like the W211 has a nearly identical trans setup to my car, a dodge charger 5.7 awd. There aren't a ton of awd chargers around so info is kind of limited on those forums. Chrysler calls the trans a nag1, but guess it's a 5gtronic/722.6 in Mercedes jargon. From what I can tell it looks like the coupling between the trans and transfer case is pretty much the same between the 4matic system and the dodge awd.

At 70k miles I had the coupler/flange between the trans and transfer case chew up the splines. Long story, but dealer didn't replace (when car was under warranty) the output shaft bearing that was failing, so I figured that was to blame for the failure.






I wound up getting a trans and transfer case from a wrecking yard with 4k miles on it (from a v8 chrysler 300). I put that in 6k miles ago last summer, so this trans and transfer case has about 10k miles now. This week taking off from a stop I got a violent shake/grind. The car would move normally under very light throttle, but completely gave out trying to go up my steep driveway (was only a mile or two from home). This time not only were those splines chewed up, but the coupler sheared off and has damaged some of the splines on the trans' output shaft.








The car makes 375hp and 400lbft stock. With the couple mods I have (intake manifold, shorty headers, catback exhaust, and a tune) it's probably not making more than 400hp and 425lbft, so not all that much more. I don't launch the car hardly ever or really beat on it. I also made sure the splines were well greased when I put the trans and transfer case together before.

Is this failure something that is seen on the mercedes cars? I'm striking out finding anyone with the same issue on the mercedes or the chrysler side of things.