Elements of English: Palatal Sounds
The English words create and quest both end with a t-sound. But add -ion, and creation ends with "shun", question with "chun". Proceed ends with a d-sound, but add -ure and procedure ends with "jur". Add -ion and the d changes to ss, so procession ends with "shun". The s in vision and pleasure is pronounced like the j in French. This book explains the principles behind these sounds and spellings.