Grinding the tops.. I hope not in the terms of chopping them up in anyways! The top mounts move up and down, if you lift your bonnet and watch the mounts as you turn the wheeel (leaning through the window :rasp
You will see them move, mine, when on lock to left or right move up and down also when on a lock when at a stand still, while moving over bumps the mounts bump up and down causing a bang noise, this is common, unless your mounts look totally worn out I wouldn't worry.. Lets see if someone else on here will join in, because I can't get the squeaky portion to make sense, but it would just be rubber+metal contacts.. Was it wet at the time?