I had a list of things that I wanted to take care of as soon as I realized they were concerns after purchasing this 2008 saturn vue xr FWD V6.. Here is one that has been on the list since day one: I noticed a rattling noise underneath the rear end of the vehicle. It is erratic so that makes it more difficult to locate/repair. It sounds like a tail pipe or muffler is rattling against another metal object. It mostly happens at a stop light when I'm in Drive. when I put it into neutral, it goes away and returns when I put the trans back into D. I have looked high and low under the car when I had it at the shop but neither the mechanic nor myself could find anything loose at the time. I don't know how to better describe it but a 'rattling noise"

The suspension is tight, all connectors to the muffler and tail pipes are secure. It seems to be on the right rear side of the vehicle. If any of you have any ideas or have had a similar situation I'd be glad to hear about it. Thanks for your reading this post and for any responses that you might send my way.

 

The heat shield for the muffler has likely lost some of the rivets with held it in place. There are only a few narrow frequency ranges that make it resonate and bump into the muffler in this case. The muffler may have the slightest bit of play and should so that the exhaust system is not completely rigid. Hence the rubber hangers to stabilize position and dissipate vibrations to the cabin.

Same thing happens with the catalytic converter heat shield.

Sometimes you just can't reproduce the sound you get at 750 RPM sitting in drive, with all four wheels on the ground.AND inspect it safely, unless you can drive it over a pit bay at the mechanics shop.

Remedy is to reattach heat shield so that it hugs the underbody as it used to. Drew a hole or two in the shield. You can use a zip tie to a nearby hole in the frame or add a rivet or two to hold it up out of the way. obviously don't use zip ties directly above the muffler or cat con.

Also, ensure that your exhaust system is physically routed properly within the channel in the underbody within which it travels. Things can get knocked around laterally, and anything halfway down the car that shifts leads to a greatly exaggerated shift further down. Meaning the entire thing may just need adjusting by half an inch somewhere further up the line to keep the exhaust system from colliding with the heat shield.

 

Derf, thanks so much for your help and insight with this. I had suspected something along these lines but I'm sure you have located it precisely. I'll take it to my mechanic and have him take a look on a lift. It's anoying but hopefully not an expensive repair. Thanks again for your response.

 

Finally had a chance to take the VUE into the shop to have the rattle checked out. A couple of welds on the muffler's heat shield solved the problem. They didn't even charge me for it. It's the same shop that replaced the water pump and the main coolant seal on the engine block just between the block and the water pump. I guess they just wanted to do a nice gesture for a new customer. Anyway I'm glad that issue is solved. It was so annoying. Thanks to Derf for his suggesting the heat shield was the culprit.

 

Glad to hear it was something simple and that you got it fixed for free. Stay with that shop.