Review on 🔊 Flowmaster 853548 Super 40 Series Muffler: Efficient Performance and Enhanced Sound Control by Jonathan Partridge

My 2015 GMC 2500HD 6.0L sounded more like a Prius than a truck of its size. Super40 took about an hour to install and what a difference. I took the time to drive the truck without the muffler after it was added and it makes it sound louder and "rougher". Starts up loudly when cold, dies quickly. Not bad at idle, squeaks when accelerating. A disgusting rumble at 50-55, and at 75 it immediately subsided. Be prepared to have about 12" of extra 3-1/2" pipe since the muffler is shorter than stock. Also, the offset was slightly offset, so the suspension had to be shortened and lengthened slightly just after the muffler. All in all a very easy installation.