>>2038726I'll mention, for Shimano there's a seal inside the freehub that you have to reuse. Not the dust seal that snaps into the hub, there's another that goes down into the freehub. For whatever reason, they consider that part of the hub, NOT part of the freehub. So if you buy a new freehub, it's going to be "missing" that seal.
This past year I swapped a bike from 7spd cassette to 10spd, and there was no way to reuse the old seal. That doesn't fit the Shimano viewpoint; they spec one replacement P/N for the hub, so of course you can reuse the old seal...
A hack solution is to take a flexible plastic lid, the kind that comes on the top of a cardboard tube (like bread crumbs, oatmeal, etc). And you can cut a seal out, to press into the freehub.
If you were to do up the cassette without any seal here, you can look down through the lockring splines and see the bearings/grease. In some sense, it's kind of shielded from the outside world, but at some point water & grit are going straight in. So this hack shit is better than nothing.
If you have to take the diy seal out, you'll have to use some kind of pick, and it leaves little 'dings', visible in the bottom pic. Go for a tight fit that's just touching on the inner circumference. Friction from rotation will quickly abrade the seal so that it no longer contacts the cone. The saying is something like, "a seal that doesn't leak, does."
Apologies if these pics are out of focus, I was probably drunk.
