We're sure we used to know the right way to say "transient", but the knowledge just seems to come and go. A really dynamic word, it can be used to describe a person who moves from place to place, an occupation that's seasonal, or even a passing mood. At its core, it just means 'temporary'.
We see the way the latter half of the word is spelled, and we're conditioned to believe that it should be pronounced a certain way, so our minds tell us to say "tran-see-ent" because of the 'i'. Even though that feels right, and to be honest it even looks right, it's not. It's "tran-shent" according to the dictionary, because even though there isn't an 'h' in the word, there somehow is in the sound. Sorry if that makes you angry. We're sure the feeling will pass.