if the engine mount is bad, when the car is at a somewhat hard turn, itll vibrate and cause a sound that seems similar to a "grinding" noise. the mount isnt the problem all the time, but it does happen enough not be a "rare case."

as for the boots...i didnt mean to take it apart, but just visually check it to see if it seems to be in decent condition.

it could be the axles...and it could be one of the engine mounts... :dunno: