I have a 2002 TL-S that has had the transmission replaced in Jan 2006. The past few months, I've noticed this weird noise when my car gets to between 40-45mph, possibly when it's shifting from 4th to 5th gear. It somewhat sounds like the car isintaking some air similar to a breathing/gasping noise. I'm not really sure what it is. It could also be grinding? Not exactly sure. This only happens around the 40-45mph range/4th to 5th gear. Also, it doesn't always happen either.

I have no check engine lights, no flashing D5 or anything like that. Would anyone know if this is something that I should bring in to get checked out?