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Flowmaster American Thunder Cat-back Exhaust System

Fits 2020-2021 GM 2500HD/3500HD with 6.6L gas engine, Crew Cab/Short Bed, Dual Out Rear/Dual Out Side, Polished Tips

Part # 817933 Be the first to write a review
Estimated shipping date: 03/10/2022
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Delta Flow
The Flowmaster® American Thunder® Cat-back exhaust system for the 2020-2021 Chevy Silverado and GMC Sierra 2500HD and 3500HD trucks with the 6.6L gas engine, has a moderate to aggressive sound level inside and outside of the truck, with all of the performance benefits you expect from Flowmaster®. Designed for the Crew Cab, Standard Bed (6.5 ft.) models only, this bolt-on, emissions-legal system features a stainless steel 50 Series HD™ muffler and large dual 3.00-inch 409 stainless steel mandrel-bent tailpipes that can be configured to exit either dual straight out the back, or dual out the sides behind the rear wheels which is best suited for towing applications. The system is finished off with a pair of large 4.00-inch polished 304 stainless steel tips and is covered by our Lifetime Limited Warranty. Designed for an easy fit, this system includes all necessary parts and hardware for installation. Notes: Fits Crew Cab with 6.5' bed length, 159-inch wheelbase only.


  • Mandrel-bent 16-gauge Tubing for Maximum Exhaust Flow
  • Uses the Factory Hanger Locations for Easy Installation
  • 50 Series HD Muffler with Delta Flow Technology
  • 409 Stainless Steel Construction for Long Life
  • Increased Performance and Exhaust Flow
  • Multiple Tailpipe Exits Provided in Kit
  • Large 3.00-inch Dual Tailpipes
  • Deep Powerful Exterior Sound
  • Lifetime Limited Warranty
  • Flowmaster Quality

About Flowmaster

Flowmaster® is a household name, and for good reason. They've built legendary exhaust systems and mufflers for decades, and now offer performance air intakes, catalytic converters, and headers to give your hot rod performance to match the iconic Flowmaster sound.

Brand Flowmaster
Catalytic Converter FormatNo
Emission Code5
Exhaust SeriesAmerican Thunder
Exit PositionDual Out Rear / Dual Out Side
Heat ShieldNo
Material409 Stainless Steel
Mount TypeUses Factory Hangers
Muffler Body Length (in)18
Muffler ColorBlack
Muffler FinishPainted
Muffler Inlet Diameter3
Muffler Inlet LocationCentered
Muffler Material409S Stainless Steel
Muffler Outlet Diameter3
Muffler Outlet LocationDual Outlet
Muffler Overall Length (in)24
Muffler Part NumberKit Only
Muffler Series50 Series HD
Muffler ShapeOval
Muffler TypeReflection
Product TypeExhaust System
Single DualDual
Sound LevelAggressive / Moderate
System TypeCat-back
Tip CutAngle
Tip Diameter4
Tip Edge StyleCut
Tip FinishPolished
Tip Length13
Tip LogoEmbossed
Tip Material304 Stainless
Tip Quantity2
Tip ShapeRound
Tip StyleDouble Wall
Tubing Diameter (in)3
Tubing Material409S Stainless Steel
California Proposition 65 Chemical NameChromium (hexavalent compounds)
Nickel (Metallic)
California Proposition 65 RequiredYes
Part Number817933

This part is legal for sale or use on Emissions Controlled Vehicles, Uncontrolled (Non-Emissions Controlled) Vehicles, and Racing Use Only Vehicles because it does not affect vehicle emissions and is not covered by emissions regulations.

Fits 2020-2021 Chevy Silverado/GMC Sierra 2500HD/3500HD trucks with 6.6L gas engine. Crew Cab/6.5ft bed only. Will not fit applications with a gooseneck hitch or overload springs.

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    Some parts are not legal for use in California or other states with similar regulations.