I have a 1999 GMC Jimmy 4x4 SLE ya I know it's not a Blazer but just about. Well anyways when it's at a cold start I hear a rattling underneath and I believe it to be my heatshield. I have heard these are affixed to the cat and not just bolted on. Is there a simple fix for this to get me buy so I don't have to replace the exhaust system as I just had to rebuild the transmission. Some tips I've heard placing u clamps around it or tach welding it. Anyone who has experience in this or a good suggestion would be greatly appreciated. Thanks in advance

 

Take it to a Midas, Tuffy, or Meineke and have them tack weld it in place if you're sure that's what's making the noise. Crawl underneath and tap the muffler with a rubber mallet or very lightly with a small hammer and see if it makes a similar rattle noise to be sure. Or there's always the visual check to see if it's loose.

 

If you have a rubber mallot or something similar you can hat the exhaust pipe and see if you can locate the rattle first. It could be loose baffles in the muffler.