[u] fronting in Californian English.
I've seen many posts here regarding the [u] fronting to [M] in Californian English. I'm Californian and just to clarify, this fronting does not occur before /l/. So for instance:
your final L is dark or light?
<<A shift from [u] to [M] isn't fronting as such, it's unrounding (though from what I've read it seems to always be accompanied by fronting in English). So you have a fully back [u] before /l/?>>
Yep. And I have to say that no Californian uses [M] before /l/.
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As Josh pointed out, changing [u] to [M] wouldn't be fronting. Do you think [}] or  might be a better transcription of the vowel you use?
My dialect does not have general /u/ fronting, but it does have breaking of /u/ (as well as all other back vowels, but it is by far most prominent with /u/) into a level diphthongs after coronals. This diphthong more conservatively is [}_^u] but is often actually [y_^u] or [iu] (I don't have this, but I often hear people who seem to pronounce /u/ as [iu] or even [ju] after coronals). In its most extreme form, it almost sounds like yod-hypercorrection, so that not only is yod-dropping reversed, but yods are added before cases of /u/ which never had them.
Note that before it (and also /U/, /w/, and /@r/) coronals are palatalized and, in the case of /t/ and /d/, may be affricated in stressed syllables; in more careful speech I have just [t_j] and [d_j] for them before /u/, but I sporadically (and particularly when stressed) affricate /t/ to [ts] and, less commonly, /d/ to [dZ]. However, I do not infrequently hear people realize /tu/ as [tSu], such as my girlfriend and in a particularly notorious lawyer's commerical here (where "twenty" was prominenly repeated a number of times with [tS_hw] rather than [t_hw] or [t_j_hw]), even though I mostly lack this.
Note though that from listening to various people from Real Life and in media content, it seems that such breaking of /u/ after coronals and resulting palatalization of coronals and affrication of /t/ and /d/ is actually not uncommon in North American English dialects.
<<As Josh pointed out, changing [u] to [M] wouldn't be fronting. Do you think [}] or  might be a better transcription of the vowel you use?>>
I'm not sure. I just use [M] because that's what Wikipedia's California English page uses. By the way, I also pronounce "juice" as [dZjMs] rather than [dZMs]. Contrast my "Jews" [dZMz].
That is interesting. We used to have a regular poster from California named Kirk, and he also said that he pronounced "juice" in such a way:
<<"juce" wouldn't be an ideal spelling for me, as I say [dZjMs]. For me, "juce" would be pronounced [dZMs], which is of course not the same.>>
<<I just use [M] because that's what Wikipedia's California English page uses.>>
Well, the article suggests that both [}] and [M] are found in California English. That's consistent with what Kirk said:
<<...is commonly [M] in my speech, even as front as [}] or  in some people's speech...>>
<<Well, the article suggests that both [}] and [M] are found in California English. That's consistent with what Kirk said:>>
Well, I'm not sure then which would be accurate. For right now, I'll just use [M]. The thing I wanted to clarify though, is that such fronting/unrounding doesn't occur before /l/. I've never heard a Californian ever pronounced "fuel" as [fjM5] or [fj}5]. An exception is "truly" which is pronounced [trMli]. This is due the vowel being at a morpheme boundry.
<<That is interesting. We used to have a regular poster from California named Kirk, and he also said that he pronounced "juice" in such a way>>
I don't know where such a pronunciation comes from, but similarly I also have [ISjM] for "issue" not *[ISM].
I have [u:] for my MOUTH vowel. This is distinct from my GOOSE vowel which is [}:].