Vibration issues

I will have to look at them again and double check all that... not something I though of thank you. One thing I am curious about my slip yoke on my drive shift has about 2 inches before the splines start inside the slip yoke. I've noticed on other drive shafts they have the splines all the way threw the slip yoke. Is there something with that that I'm not catching that could also be causing an issue?