What doe you mean by "signifcant threads"? The Uniglide version of Shimano freehubs had external threads at the outboard end, to accommodate the thread-on outer cog. When they went to Hyperglide, all the cogs were splined and held on by a threaded lockring that engaged internal threads on the freehub body. During the transition era some had both the internal and external threads, with the ability to use either Uniglide or Hyperglide cassette sprockets.