The Mercedes needed a new left driveaxle. One of the CV boots had gone and steadily increasing driveline vibration told me it wasn't going to last much longer. I'd been putting it off a bit because the job is a messy pain in the ass; unlike more modern cars where you can just unbolt the CV joint from the drive flange on the diff, on this one the differential has to be opened to remove a circlip that retains the axle's splined shaft inside the diff.
All things considered it went fairly smoothly. The fill plug in the diff turned out to be stuck — very stuck, I'm guessing, since someone had managed to mostly strip the 17mm internal hex. I ended up refilling the diff through an air vent on the top. This worked but was slow, and I ended up wearing some of the gear oil on my arm because I had to keep lifting the hose out to let the air out as I added oil. If you've never experienced the smell of hypoid gear oil, let me just say it is not quickly forgotten. It has a strongly sulfurous smell, a bit like someone startled a skunk while it was bathing in used motor oil. By the time I was done I smelled like it, the garage smelled like it, and the hallway outside the garage smelled like it...
The hardest part of the job was actually getting the circlip back on the axle. It was far too big for my circlip pliers, and in too restricted a spot to really get to with circlip pliers anyway, so I had to resort to tapping it back into place with a punch. Every time I got it crooked it popped back out and landed five feet behind the car. It took about two hours, but eventually my persistence won out.
I had already planned to replace the diff mount, which also serves as the rear subframe support, because it has to come out to do this job anyway. I'm glad I had a replacement on hand; the old mount turned out to be bent. Not sure how they managed that...maybe by jacking the car up by it with a very heavy load in the back? Anyway, this probably explains my uneven rear tire wear.
Tip: When you have to support something like a differential or engine while removing/reinstalling a mount, use a scissor jack instead of a hydraulic jack. It gives you much finer up/down control and it won't slowly sink under load.