I’ve been a Flowmaster guy for about as long as I’ve been messing with cars. My first Camaro promptly ditched its Cherry Bomb glasspacks for a pair of 40 Series mufflers. Not long after I purchased my second Camaro, it got the same treatment. Then, after I eventually decided the first car wasn’t obnoxious enough, I welded up a pair of Super 10s.
Naturally, when Holley gave me the opportunity to bolt a Flowmaster cat-back onto my daily-driven 5.3-liter Silverado, I didn’t need much convincing. But there was one catch: I didn’t want my truck to sound like my Camaros. The ‘fun’ cars can rattle windows and generally make questionable amounts of noise. But the Silverado has to haul parts, cover road trips, sit in traffic, and occasionally leave the house before the rest of civilization wakes up. In short: I wanted that familiar Flowmaster rumble without spending hours on the highway listening to it drone inside my skull.
After listening to Flowmaster’s sound clips, I landed on the company’s American Thunder Cat-Back Exhaust System for 2019–2026 5.3-liter Silverado 1500s (PN: 817895).
More Attitude, Not More Headache
Flowmaster calls the American Thunder system “moderately aggressive,” meaning an aggressive exterior tone with more restrained interior noise. The bolt-on system uses 2.5-inch stainless tubing feeding a stainless Super 40 Series muffler, along with welded hangers, flat-band clamps, and four black ceramic-coated 4.5-inch stainless tips.
Installation is relatively straightforward, although removing GM’s enormous factory exhaust assembly is considerably easier with a lift. We handled the job at ForgeSpeed in Mooresville, North Carolina, where having the Silverado in the air allowed us to remove the intermediate and passenger-side pipe without introducing it to a hacksaw.
One useful discovery involved the factory ‘USB port’ exhaust tips. Rather than fighting them from underneath the truck, we removed the step assemblies from the bumper and gained direct access to the three bolts securing each tip. Since my Midnight Edition Trail Boss came with optional powder-coated tips, this also allowed me to stash them away like the automotive hoarder I apparently am.
From there, installation was basically a matter of bolting the Flowmaster intermediate pipe to the converter using the factory clip, hanging the Super 40, assembling the dual tailpipes, and adjusting everything until the four tips sat properly in the bumper.
Just Enough Thunder
The payoff is exactly what I wanted. At idle, the 5.3-liter LT already has a pleasant V8 burble, and the American Thunder system simply gives it more authority. Put your foot into it and that familiar Flowmaster rumble fills the cab, but once the truck settles into higher gears, the exhaust quiets down enough that long highway trips don’t become an endurance test.
After more than 1,000 miles, I think Flowmaster pretty much nailed the daily-driver balance. The Silverado finally sounds like a proper V8 truck without pretending it needs to wake up the entire neighborhood every morning. After all, I have my Camaros for that job.
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