Last year or so I put Hooker BlackHart axle backs on my car. For the past three months or so, the exhaust would make a rattle sound if I drove the car spiritedly. If I drove legit, I would not have the rattle. So I did research and obvious common since told me that it had something to do with axle backs. As part of my research, I discovered that the exhaust will expand under heat blah blah.
I had already checked the axle backs once, when the car was on ramps, but I didn't see anything weird but I did discover my pinion seal was leaking.... but I digress.
I checked again last week and I noticed the hangers closest to the bumper were to close to my hitch. So we have hangers too close, heat makes things expand..... 1+1=2 lol.
So I used the same product mentioned by YutStang and it's been several days and no rattle noise. If the material eventually wears out, for my application, I'll probably get some rubber tubing and slice one side and slip it on a zip tie it up.... I don't have to worry about heat as much so I think that would work great too.