Jonny69
Senior Retro Guru
That's not quite correct. They're both HG freehubs because as the others said there's no external thread. The 7-speed Uniglide/Hyperglide compatible freehub looks like this:Left side is Uniglide/Hyperglide compatible + the old little bit of threading at the end, Right is newer style Hyperglide. 7-speed cassette will fit on the newer one (+ a shim between the spokes and backside of cassette), but the 8-speed cassette will NOT fit on the older one because the cassette is wider than the old freehub body. Sprocket spacing between each other and within a 7-speed and 8-speed cassette are the same.
The only way to use the Uniglide/Hyperglide freehub and get 8-speeds is to sort of build your own cassette using a 10-speed cassette with the much narrower spacing between sprockets and the slightly narrower sprockets. Though, this may be cost prohibitive to get the gearing you want as it may take two 10-speed cassettes, or buying individually. Or alternatively (and maaaaaaybe) you can use the 8-spd cassette with 10 or 11 spd spacers so as long as your overall width is the same for that old freehub.
See it has the external UG thread as well as the internal HG thread and has one narrow spline for the HG cassette.
You can put 8 speeds on this freehub by using a 9-speed HG cassette with one cog and spacer taken off, or put 9 speeds on it by using a 10-speed HG cassette with one cog and spacer taken off. Easiest cog to take off is the the biggest one at the back. Use a cassette where all the cogs are separate and not rings riveted to a cage, and you can take the biggest one off like this. If you want to take the smallest one off, you'll need to make up a ring out of 2mm wire to sit in the recess in the next one up or it won't tighten up.