I taught English language in Japan. English was my favorite course study and is indeed one of the most difficult languages to learn. They'd would be pronounced sounding like "theid". Depending on the sentence structure it could mean "they did" or "they would". Not sure I'm answering your question or merely contemplating it.
Answer from Jennifer Kolhagen on Stack ExchangeVideos
I taught English language in Japan. English was my favorite course study and is indeed one of the most difficult languages to learn. They'd would be pronounced sounding like "theid". Depending on the sentence structure it could mean "they did" or "they would". Not sure I'm answering your question or merely contemplating it.
There is no other pronunciation for "they'd" than /ðeɪd/, whether in BrE or AmE. This is the pronunciation used by the speaker, but the second part of the diphthong is only faintly heard.
(Cambridge Dictionary) they’d How to pronounce "they’d"
UK/ðeɪd/ US/ðeɪd/
This is also the only pronunciation in Longman Pronunciation Dictionary (J C Wells).
In normal speech the sound is weaker; this can be heard in the spoken sentences of a pronunciation model on You Tube; the sound of the second vowel in /eɪ/ becomes much attenuated when found in a full sentence; it is barely audible.
How to pronounce "they'd" in English
How would yall say it? Do you Not pronounce the D sometimes, or is there a "d" there even if you're speaking fast
I only ever hear this from people who are 50+ years old; yesterDEE, friDEE, tuesDEE. It's really common.
Where did this come from?