What would cause my car to make a hollow noise when driving

Congratulations! your engine is broken in !!!!!!!
You have nothnig to worry about that is diesel technology. If your truck made it this far you have a lifetime of joyful riding ahead of you.

More than likely that is EXACTLY what it is, something has fallen into the Hollow of the Door and you NEED to found out what is it. Since it has started and not a new Car with a NEW Issue, you need to not only discover what is causing it but also what Broke inside the door.. Prolonged not finding out what it is could cause your window to break, the Lock/Handle to be inop and a few other things... Clip not a big deal, Nut or Bolt, moreso

could be tyre noise try with your spare if its a different make and see if makes a difference

I have heard a lot of descriptions for brake noises but the term hollow does not bring anything to mind. Can you be more specific about it? Does it happen when you stop? Can you apply just the parking brake and see if it happens?

Could be catalytic con.in side.

HI Cindy
The noise you hearing is the rear end bearings going bad
you should get them replaced as soon as possible
the longer you drive on them the more damage you do
and they could lock up

The high idle could be causing the noise - or it could have a vac leak. I would check the computer for trouble codes first.
Could have a faulty O2 sensor or map sensor - depending on that possible vac leak.

It is very likely the exhaust system doing this, put it on a car lift and check for the noise.

it means that you need to research either a different car, or a different engine for this car. A loud knocking noise indicates a connecting rod is loose, and your engine has little to no time left before the rod or endcap breaks, completely messing up your engine, and making it very difficult to change. If you must drive it, drive it slow, and be super gentle with the gas...like you're driving on ice. If it's more of a ticking noise, that could be a lifter, but a loud hollow sounding knock is a rod. You may also have a check engine light showing up on the dash from the knock sensor.

check the fluid in the rear. We just replaced a rear on the same exact vehicle. Does it hum going down the road? Does the humming increase with speed? Also check the exhaust. Chrysler products are famous for their ratteling exhaust.