is always a good place to look and see if there was a recall issued on your car.
Not trying to be a wise guy Ed, but it is really hard to diagnose a noise from inside the car itrslef, much less when it's going downhill
What has me concerned Ed is that it only happens "from time too time", and it has two different noises.....a grinding is usually metal against metal...a squealing would make me think a rubber "something" was rubbing......but where?
My advise Ed is this........if you feel safe driving it, and you can put up with the "squealing/grinding"
noise....then don't fix what ain't broke. Otherwise, if it bothers you enough that you fear for your safety, or the safety of others, make an appointment right away at where you take the vehicle for being diagnosed and repaired.
I know it wasn't much help Ed, but thanks for giving us at FixYa.com a chance to work for you.