My '05 spark arrestor was externally screwed to the end. Some others models are internal and become clogged - usually removed by the owners. If you have an internal one then it should be some bolts visible there for access to it. Mine promptly fell off when the screw came out of the tailpipe end . The heat guard on mine used to rattle (it says hot on it)and is visible with the cargo bed up. There is also a small safety shield between the fan and muffler that will rattle sometimes. There is a allen plug in the bottom of the muffler that is used to remove soot from it. It is unscrewed, the engine revved and then replaced. The procedure is mentioned in the owners manual. Some folks never do this though and it shouldn't be a noise maker. Does the machine rattle when in motion or just at idle?. The drive shafts rattle like crazy on these models too. If they have never been replaced , that may be the source. The rear shaft is very near the muffler. An egg shaped bearing called the carrier bearing connects the front and rear shafts on the all but the new '11 models. Sometimes, it will go out when the shafts are worn and produce noises. I get under mine every so often with the machine off and wiggle,poke and prod to see what is moving and shouldn't be. Then , I look at it with it in park with the motor on and see what gives. How many hours are on it? bordercollie