Modern English Vowel Shortenings

Are there any rules to account for the shortening of Modern English -
ood and -ead?

-ood has three developments:

/Vd/: blood, flood

The same development is seen in: brother, mother, glove, plover,
does. There may also have been a similar development in: honey,
coney.

/Ud/: good, hood, -hood, stood, wood.

The same development is also seen in: foot, soot. _wool_ derives
from OE _wull_, and _poof_ and _woof_ (of a dog) appear in the 19th
century. _could_, _would_ and _should_ might belong here. I
actually pronounce _tooth_ /tUþ/, but that is a personal
idiosyncracy.

/u:d/: brood, food, mood, rood

I exclude _lewd_, _rude_, _shrewd_ because the vowel was /jU:/. I
exclude _drood_ as slang and probably recent. I have excluded
regularly formed derivatives.

There is a well-nigh lexicon wide shortening of -ook to /Uk/. (It
is far from geographically universal - even North Midlands (UK)
speech lacks this shortening.)

-ead has two pronunciations:

/ed/: bread, dead, dread, head, lead (n.), meadow, read (past),
ready, spread, stead, tread
/i:d/: bead, beadle, lead (v.), mead, plead, read (present)

Shortening is also known before /þ/:

/eþ/: breath, death
/i:þ/: heath, wreath

Before /ð/ we have:

/eð/: feather, leather, weather
/i:ð/: breathe, heathen

Before /v/ we have:
/ev/: leaven
/i:v/: cleave, leave

Before /Z/ we have:
/eZ/: treasure

Cf. <leisure>, which is /leZ&/ (UK) or /li:Z&r/ (US)

Before /t/ we normally have /i:/, but with /e/ we have: sweat.

In derived forms ending in two consonants, we have /e/, e.g. past
forms in -t (dealt, dreamt, etc.), health, wealth. Perhaps this
accounts for: heart, hearth, learn, yearn; beard, hearse, pearl,
realm, search. However, note <weald> /wi:ld/.

Utterly sporadic are the shortenings in: deaf, pleasant, weapon.

Richard.