In Sindarin and Noldorin, any final v originating from either m or b became w after the diphthong ae. There are numerous examples and only one possible counterexample, namely S. raef “net” as an alternate to raew, which Tolkien said was a blending of Q. raima “net” and raiwe “lace” (VT42/12). However, it is possible in this case that raef is archaic and raew is the modern form.

There are also a couple of Sindarin examples of v > w after the diphthong oe: S. oew “evil deed” < ✶okma and S. lhoew “poison” vs. Q. hloima. There are no such examples in Noldorin, which is a bit odd since frequently Noldorin primitive ai became oe, but the development to oe was inhibited when the final vowel ended up being w, so the combination oev was apparently rare to non-existent in Noldorin.

There are also a few examples in The Etymologies where v > w after the simple vowel i (short or long):

• N. hiw “sticky” < ᴹ✶khīmā (Ety/KHIM).
• N. cíw “earth” [deleted] < ᴹ✶kēm (EtyAC/KEM) [replaced by N. coe].
• N. tîw “letter” < ᴹ✶tekmē (Ety/TEK) [the mechanism where ek > ei > ī isn’t clear].

On the basis of these examples, David Salo posited that final v became w after the high vowel i (GS/§4.173, GS/§4.174), though he posited that this sound change occurred earlier, before ṽ and β (from m and b) blended into [v]. Unfortunately, we have a Noldorin counter-example (published after Salo’s Gateway to Sindarin) that clearly shows [ai] > [ae] before [v] > [w]:

• ON. sagma > saʒmh > sae̯mh > saęw “poison” (PE22/32).

Furthermore, there are numerous Sindarin examples (and a couple Noldorin examples) where v (spelt f finally) survived after i, with several of the Sindarin examples published after Salo’s original research:

• S. îf “cliff” < ✶īb- (PE17/92).
• S. lîf “link” < ✶limi (VT47/6).
• S. nîf “phantom” (NM/238) [maybe < √NIM].
• N. nîf “front” < ᴹ✶nībe (Ety/NIB).
• S. rîf “bark” (LotR/474) [etymology unknown].
• N. rhîf vs. ᴹQ. ríma “edge” (Ety/RĪ).

The only possible Sindarin counterexample is S. rhîw vs. Q. hrívë “winter” (LotR/1107), but these may be derived from *srīwē; compare S. cîw, Q. céva “fresh” < ✶kēwā (VT48/8).

On the basis of these examples, I think it likely that by the Sindarin period, v > w only after the diphthongs ae and oe, and surviving otherwise.

Conceptual Developments: In Gnomish of the 1910s the sound change [m] > [v] did not occur, so there were far fewer potential examples of [v] > [w], making it difficult to analyze this sound change. There is even one example that seems to hint at a reversed development of [w] > [v] or [f]: ᴱ✶duiwe > G. duif “stream”, extended forms duivrad “canal” and duivrant “aqueduct” (GL/31). Lack of examples make the phonetic developments of the Early Noldorin of the 1920s hard to analyze as well.

GS/§4.173 GS/§4.174 but S. raef @@@