Take your Journey to another dealership for sure. If it's only when you're moving it's much more likely something to do with the drivetrain as opposed to the engine. My best guess is that when they did the brakes the mangled something else up.

When you apply the brakes what happens to the grinding sound (does it sound the same or does the grinding sound change)? Additionally can you get the sound to change by doing anything else (turning right or left - loading the suspension, etc.)?