A good place to start is by inspecting the engine mounts. If one is collapsed, it can let that end of the engine hang down a little, and that can allow a pulley to rub on something. This is easier to determine too when you are familiar with the vehicle, as in having worked on a lot of them so you know what "normal" looks like. The mounts also limit the amount the engine can rock back and forth between shifting between reverse and drive, and between accelerating and coasting.
Sometimes you can get a clue to this by looking for shiny rub marks on shields where a pulley has been rubbing.
There can be some other unusual causes of this type of noise too. For example, some emissions system valves turn on during coasting, and a hose related to them could have a leak. To find things like that, consider looking for a tool called a "chassis ear". You might find one at an auto parts store that rents or borrows tools, but be aware that a lot of mechanics have never seen or even heard of this tool. It is a set of six microphones, a switch box, and headphones. You clip the microphones to suspect points, then drive around while listening with the headphones. You can move the microphones around to zero in on the source of the noise. Suspension and alignment mechanics use it to find rattles, squeaks, and other noises.
Friday, June 23rd, 2017 AT 3:23 PM