I was struggling with adding the carousel component to Bootstrap 4 and found a minor change.

"item" in Bootstrap 3 is now "carousel-item" in Bootstrap 4.

Here are some other differences...
http://www.quackit.com/bootstrap/bootst … trap_4.cfm

Check out a rough draft of my Bootstrap Carousel which includes CSS Animate and JavaScript add on that gives control of delay and duration.
http://gluexp.coffeecup.com/index.html