Often you can see it if it's bad... like rubber spaghetti flaking off.Originally Posted by mamilapon
I've never had one so bad I could FEEL it... but I imagine if it failed you would know it right away. Driveline vibration under load would lead me to inspect it - pretty easy, just get your eyes under the car and check it out. If it looks 100% intact, I would look at other things as being a source of trouble, center bearing, tranny mounts, etc. depends on what symptoms you're seeing.