When French words were imported into English, their pronunciations where modified to fit English phonology, orthographical and intonation patterns, hence making them seem more 'English'. This is not exclusively the case with Norman loanwords, the word 'garage' has undergone a similar shift from being pronounced /gɘ'ra:ʒ/ to being pronounced /'gæridʒ/, and English loanwords into French also undergo similar pronunciation shifts.

That is not to say, however, that Norman French did not differ from Parisian French, and that this had no effect on loanwords into English. For example, words ending in -aire or -oire in Standard French were replaced with the suffixes -arie and -orie (I'm not sure about the orthography but that's how they were pronounced anyway) in Norman French, hence why we talk about salary and history, and not salaire and histoire as in Standard French. Normandy was also north of an isogloss known as the Joret line, while in the dialects south of this line, the sounds /k/ and /g/ would have been softened to /ʃ/ and /ʒ/. This is why we talk about the cat being in the garden, and not the chat being in the jardin, as in modern French.