actual, affrication, stressed syllables, u

t and d in the coda of a stressed syllable, u and affrication (choo, joo) are tightly related.

Take a two syllable word that has a form: CV[t/d]u, CCV[t/d]u, V[t/d]u, etc where the stress falls on V.

In this pattern, t and d get weakened or go thru lenition or get affricated.

atu:con-'grat-u-la-tion
adu:'grad-u-al
etu: 'pet-u-lant
edu: 'ed-u-'cate
itu: 'sit-u-a-tion
idu: 'in-di'vid-u-al
otu:'clot-ure
odu:'mod-u-le
utu: 'mut-u-al
udu: none that I know of

In lento, you can delete the "wuh" syllable, you get "wuh" because of "ua" cluster. This is called sonorant gemination.

Let me explain with one word actual:

act-u-al
'æktʃə-al (affrication thanks to the structure explained above)
'æktʃəwəl (sonorant /w/ gemination)
'ækʃəwəl (deletion of /t/ in some dialects, lento tempo)
'æktʃəl (in the fast/casual speec/allegro tempo/lower register:synope of the sonorant, its called degemination)
'ækʃəl (deletion of /t/ in some dialects, masks vs mass)



you can apply the similar processes on these words: mutual, ritual, individual, sexual, intellectual, manual.

The point is this: your typical pronunciation books don't go this far. And speech you hear can be analyzed this way, with the help of intonemes and preintomenes.