"Has anyone actually experienced these supposed "vibrations" that can shed some light on what they might feel like or when they may occur so those of us without the shakers can determine if we in fact have them? "
I have not but I can tell you a story that may have something to do with it.
My dad bought his bird new in '67, and only had it 5 years. As a kid (born in '62) I thought the bird was the coolest car ever( I was rather advanced for my age). At the time we lived in the DC metro area so my dad drove the capitol beltway every day it used to have "seams" or expansion joints pretty close. I can recall news stories of them buckling and causing a lane to close. Anyway, when I asked Dad why he got rid of the bird he said that when he would drive over those "seams" the ask end of the bird would change lanes and pass him. He kinda said it jokingly but he did have 2 large lead bricks that he kept in the trunk to help keep the rear in check. ( someplace a large scintillation counter is missing it's shields)
I assume he had the shakers unless some early birds didn't get 'em ?
His experience may not have anything to do with shakers but along with information from others perhaps it will help?
