S. final [w] usually became [u]; [-C{vw}|-aw] > [-Cu|-au]
In both Sindarin and Noldorin, where it was not otherwise lost, a final [w] usually became [u], mostly notably after a consonant as described by David Salo (GS/§4.195). In Tolkien’s writing, he sometimes represented this final [u] as -w, but this seems to be an orthographic convention, not the actual pronunciation. He mentioned this sound change a number of times:
S. final [vn] sometimes became [von]; [-C{vw}|-aw] > [-Cu|-au]
In Noldorin, there are several examples where a final [-vn] became [-von]:
S. final [l], [r] usually became syllabic; [-C{lr}] > [-Co{lr}]
In both Sindarin and Noldorin, a final [l] or [r] after a consonant usually became syllabic, and developed into [-ol] and [-or] respectively, as noted by David Salo (GS/§4.192). There are a large number examples in both Sindarin and Noldorin:
S. long voiceless spirants shortened; [θθ|xx] > [θ|x]
In both Sindarin and Noldorin, long voiceless spirants shortened, as noted by David Salo (GS/§4.184). Tolkien alluded to this phonetic development in a discussion of the transcriptions used by Ælfwine in his document on the Feanorian Alphabet from the 1930s:
S. [h] vanished after vowels; [Vh] > [Vø]
In both Sindarin and Noldorin, any non-initial [h] vanished after vowels, as noted by David Salo (GS/§4.100, GS/§4.107, GS/§4.116). A similar sound change occurred in Welsh (WGCH/§94ii). This sound change primarily applied to the [h] that developed from intervocalic [s] which therefore ultimately vanished, as described by Tolkien in a note in The Etymologies from the 1930s:
*Minaþurindor *entankatánier sa i *rando Silindo láne illume silúmea nómeryasse mi i *Anarya *Panasta.
Nóna ve helka rando amna *kanallume háya pella silúmea nómerya, Silindo rongo *menune alta lendaryanna ya xéyane tere koranari ototuxa húme tenna anyane i nóme imbe Karnil ar *Kormanil. Si enwa entankataina ló i kendare *pityarandoron kombion atta i *pepellar Anar epe ar nó Silindo imya rindesse. Tana pityarandoron ére áne i *sinwasse pá i rando ranya.
S. [ou] became [au]; [ou] > [au]
In both Sindarin and Noldorin, at a late stage of the language, the diphthong [ou] became [au], as noted by David Salo (GS/§4.110). This development is more straightforward in Noldorin, where primitive [ou] also ultimately developed into [au]:
S. final [w], [v] vanished after [u]; [-u{vw}] > [-u]
In Sindarin and Noldorin, any final [v] or [w] after the vowel [u] vanished, as noted by David Salo (GS/§4.173, GS/§4.176, GS/§4.177). The likely mechanism was [v] > [w], and then [w] became [u] which blended with the preceding vowel. This sound change also occurred after the diphthong au, as noted by Tolkien himself:
S. final [v] became [w] after [i], [ae], [oe]; [-{ae|oe|i}v] > [-{ae|oe|i}w]
S. [mm] shortened; [mm] > [m]
