On Aug 20, 12:51 pm, "john.kara...@gmail.com" <john.kara...@gmail.com>
wrote:

Is the sound continuous or just immediately after start up? You threw
me when you mentioned the part about the shifting. If it's a grinding
noise that only occurs immediately after start up and only after the
car has sat for a while, I would suspect an oiling problem. I would
switch motor oils to a higher quality one and also try a higher
quality filter. Some of your cheaper filters omit the check valve that
keeps the oil up in the engine when the vehicle is not running. Having
said that, some cars are famous for that by design. My Suburban 5.7
did it all the time. I tried everything 20W50, K&N oil filters, etc. I
finally read a TSB where Chevy claimed this was "normal".

As far as your humming goes, I would suspect tires before I suspect
brakes. I don't know what the O.E.M. tire is on your vehicle but
manufacturers have gotten pretty stingy about putting good quality
tires (Michelin) on new vehicles. Some of them are pretty crappy. Try
having your tires rotated and balanced. If you recently had them
rotated that might be the problem. If the tires that are now on the
front stayed on the rear too long they might have become feathered.
This will definitely translate to noise/slight vibrations when you put
those tires on the front.