There is a class of words, mainly such as
the, this, that, these, those, though, although, then, there, thus,
the archaic thou, thee, thy, thine, thyself, thence;
which I always find myself pronouncing with a stopped sound intermediate between a "d" and the smoother (fricative) sound of "th" in words such as
father, mother, brother, other, bother, rather, feather, dither, breathe, loathe, smooth.
This seems fairly common in American English, but many people always pronounce a voiced "th" smoothly, and some think that speech that sounds too much like "dis, dat, deze, doze" is uneducated or not correct. This pronunciation seems to push the "d" further back toward the "r", (for distinction's sake?) and the "r" even further back, deep against the soft palate.
I'm curious as to where and when this slight consonant shift has taken place in English, and where it is considered standard or not, as the case may be.