A few years ago, I saw a complete 6-cylinder engine & 4-matic transaxle unit crated-up outside the parts dept at my local Mercedes dealer. It obviously came out of someone's car.
No idea if it was being shipped back for a warranty claim, or why both engine & transaxle needed to be replaced as a unit, exept that the differential seemed to be built into the oil-pan.

Happy Motoring, Mark

__________________
DrDKW