Pronunciation of past tense '...ed' endings

BASE VERBS ENDING IN /t/ or /d/

wait, start, treat, test, date, guard, decide, fade, heed, add, mend  
change to /Id/ >>
waited, started, treated, tested, dated, guarded, decided, faded, heeded, added, mended

WHY? When two consonants sounding very similar of the same place and manner are next to each other it is impossible to distinguish them from one another. You need to separate them with the vowel sound /I/ so you can hear the difference between them. e.g /…dId/

BASE VERBS ENDING IN VOICELESS CONSONANTS, EXCEPT 't'

work, cook, miss, pass, guess, face, chase, race, joke, ask, bounce, fix, tax, crash, wash, watch, fetch  
change to /t/ >>
worked, cooked, missed, passed, guessed, faced, chased, raced, joked, asked, bounced, fixed, taxed, crashed, washed, watched, fetched

WHY? If the base verb ends in a voiceless consonant that sounds different to the end sound of the base verb (not the same »place and manner, no vowel sound is needed to distinguish between the two sounds, as they already sound different; e.g. /…kt/

BASE VERBS ENDING IN VOWEL SOUNDS OR VOICED CONSONANTS, EXCEPT 'd'

care, bore, argue, allow, move, dive, curve, believe, cycle, file, boil, cancel, climb, turn, learn, beg, bug, judge. 
change to /d/ >>
cared, bored, argued, allowed, moved, dived, curved, believed, cycled, filed, boiled, cancelled, climbed, turned, learned, begged, bugged, judged.

WHY? If the base word ends in a vowel sound or a voiced consonant that sounds different to the end sound of the base verb and is not the same place and manner, no vowel sound is needed to distinguish between the two sounds, as they already sound different; e.g. /…gd/