I recently got an old KitchenAid mixer from a friend. It's a k45ss, from maybe the early 80s, and the general advice I see is that with typical home use they should be regreased every ~10y. I ordered 4oz of food-safe synthetic grease and followed Mr. Mixer's YouTube guide (parts 1, 2, 3). With my phone playing the videos I followed along: opening the mixer up, removing the old grease, adding the new grease, and putting it back together. There were slight differences (my strain relief was annoying, and I didn't have a pin inside the gear assembly and needed to remove the worm assembly first instead) but it was pretty close.

The planetary gear assembly was pretty low on grease, and the grease there was a bit dry:

The upper area had more grease, though the grease was a harder than I expect it was supposed to be:

The gears were in good shape, and were nice and solid feeling.

Degreasing, regreasing, and assembly went fine. Probably 1.5hr all together? When I was done, however, I realized I had a part left over: one of three washers.

I looked back over the video, and it talked about installing two of these washers, which I remembered doing, but I was stumped by how I ended up with a third. There wasn't any logical place which should have a washer but didn't.

I talked about this at dinner, and one of my housemates said they also had an old KitchenAid that had probably never been regreased (k45, cord isn't grounded, maybe late 60s). We decided to do theirs together, and maybe we'd see where the washer went.

The combination of having a second pair of hands and having just done one the previous evening made it go a lot faster: less than an hour. Very similar to mine, except the strain relief was even more annoying. We did figure out the washer mystery, though: there are two washers in the planetary mechanism, stacked on top of each other.

I'm not sure whether it's worth opening the bottom of mine back up to install the extra washer. I'm leaning towards yes (they wouldn't put in two washers for no reason, doesn't require taking the whole thing apart) but possibly I don't really need to?