Flowmaster
Flowmaster 20-25 GM 2500/3500 6.6L GAS Direct Fit FlowFX Muffler
Flowmaster 20-25 GM 2500/3500 6.6L GAS Direct Fit FlowFX Muffler
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Flowmaster's® Flow FX Direct-Fit Muffler exhaust system for the 2020-2026 GM 2500HD and 3500HD trucks with the 6.6L gas engines gives you a great value packed way to help you customize your GM truck to your personality. This performance muffler system fits both 2/4 Wheel drive models and is manufactured from 409 stainless steel for years of trouble-free service and performance. Features include a 3.50-inch inlet pipe leading into a 409 stainless steel Flow FX series "straight-through" muffler for great sound and maximum performance and no drone. The muffler then connects to the factory tailpipe for a simple and effective performance upgrade. Max dyno gains of 7 hp and 5 lb-ft at the rear wheels. This results in better acceleration and towing performance. The system uses all the factory hanger locations and connections for an easy installation that you can do at home. Kits include installation instructions and all necessary hardware. Backed by Flowmaster's Lifetime Limited Warranty.
- A tuned Flow FX style muffler delivers a deep, aggressive to moderate performance tone and improves exhaust flow with no drone
- Kit includes complete hardware and factory styled hangers in the stock locations for an easy installation
- 3.5-inch mandrel bent 16-gauge 409 stainless steel tubing maximizes exhaust flow and improves durability
- Max increases of up to 7 hp and 5 lb-ft over the stock exhaust at the wheels
- Tuned performance muffler eliminates interior drone
- Maintains factory warranty
- Lifetime Limited Warranty
Vehicle Fitment
- 2020-2026 Chevrolet Silverado 2500 HD
- 2020-2026 Chevrolet Silverado 3500 HD
- 2020-2026 GMC Sierra 2500 HD
- 2020-2026 GMC Sierra 3500 HD
Please verify exact fitment for your trim and engine before ordering.
🚚 Vendor Direct Shipment: This item is not stocked in our warehouse and ships directly from the manufacturer. Please allow additional handling time before dispatch.
Manufacturer Part Number: 718155
Images are for illustrative purposes only. Actual product may vary.
⚠ WARNING (California Proposition 65): This product can expose you to chemicals which are known to the State of California to cause cancer and/or birth defects or other reproductive harm. For more information go to www.p65warnings.ca.gov.
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Manufacturer's Warranty — Flowmaster
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Manufacturer's Warranty — Flowmaster
Flowmaster warranty is tiered by material and product line. Lifetime Limited Warranty — stainless steel mufflers (FlowFX series excepted), all stainless steel exhaust systems (FlowFX included), stainless steel pipes, air intake kits and oiled-type filters (cleaning kits excepted), and other stainless steel exhaust accessories (exhaust tips and racing products excepted); this runs for the life of the original vehicle the part was installed on. Three (3) years — aluminized steel mufflers, exhaust systems and pipes, all exhaust tips, other non-race exhaust accessories, and commercial-vehicle applications of aluminized or stainless products. Two (2) years — Delta Force dry air intake filter elements. One (1) year — FlowFX series mufflers, Elite Series headers, and electronic components such as Delta Boost modules. Catalytic converters sold under the Flowmaster brand are excluded from this warranty. Coverage runs from the date of original purchase, to the original purchaser only, and only while the part remains on the vehicle it was originally installed on. Header coverage does not extend to damage caused by exhaust insulating wrap and is void if the header was fitted to a new or rebuilt engine during the initial break-in period. Sound-absorbing material inside “straight-through” mufflers degrades over time; Flowmaster treats that as normal wear, not a material defect. Also excluded: interior and exterior sound levels, cosmetic issues such as coatings and material discoloration, installation on a racing vehicle, improper installation or installation contrary to Flowmaster instructions, alteration, misuse, repair, accident, collision, undercarriage road impact or debris, and willful or negligent acts. To claim, the original purchaser returns the product either to the original retailer or directly to Flowmaster — a Returned Material Authorization (RMA) number must be obtained from Flowmaster first if returning to them — with proof of purchase showing place, price, product and date. Flowmaster's remedy is exchange for the same part number or refund of the purchase price at its option; installation, labor, towing and shipping costs are not covered.
Warranty terms are set by the manufacturer and may change. Full details and claims are handled directly by Flowmaster. Contact us if you need help with a warranty claim.

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