The pronunciation of 'do you' and 'did you'

[joham]

Dear sir/madame, I was reading and listening to the book AMERICAN ACCENT TRAINING (by Ann Cook) and wondered why in fluent English 'do you' is pronounced as 'dyu' while 'did you' is respectively pronounced as 'joo', 'ja' and 'ju' (and they sounded to me roughly no different) . How comes that, could you tell me? Thank you in advance.

What do you think? Whaddyu think?
What did you do with it? Whajoo do with it?
How did you like it? Howja like it?
When did you get it? When ju geddit?

 

[5jj]

There is very little difference in the pronunciation of the 'do' and 'did' forms for some speakers in casual conversation. Context tells us what is intended.

Why? In informal speech we often run things together. It's normal and natural.