that is exactly what ABS is like when in effect...
vibrating/crunching....
if this ever happens in an emergency...
relax... you will not lock up and will still have "some" control of the car... that is why ABS is a good thing...
practice/test it in a safe place...
get used to the feel of the abs.. so that you dont "panic" when it kicks in....
you can be in full ABS mode and still turn/control the car.. it is amazing...
try this on a closed off - empty - desolate area...
from a stop... get up to about 40mph... hit the brakes HARD... and turn the wheel as if to avoid something.. at the same time...
you are still in control!!! do that a few times and you will have no fear of your ABS and will be ready to use it when the time comes...
j.