Search  for anything...
Flowmaster

Flowmaster 818121 American Thunder Axle-Back Exhaust System Stainless Single Exit

  • Based on 10 reviews
Condition: New
Checking for the best price...
$481.95 Why this price?
Save $41.88 was $523.83

Buy Now, Pay Later

As low as / mo
  • – Up to 36-month term if approved
  • – No impact on credit to apply
  • – Instant approval decision
  • – Secure and straightforward checkout

Ready to go? Add this product to your cart and select a plan during checkout.

Payment plans are offered through our trusted finance partners Klarna, Affirm, Afterpay, Apple Pay, and PayTomorrow. No-credit-needed leasing options through Acima may also be available at checkout.

Learn more about financing & leasing here.

Free shipping on this product

FREE 30-day refund/replacement

To qualify for a full refund, items must be returned in their original, unused condition. If an item is returned in a used, damaged, or materially different state, you may be granted a partial refund.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

Availability: 12 left in stock
Fulfilled by Amazon
Arrives Wednesday, Jul 1
Order within 14 hours and 15 minutes
Available payment plans shown during checkout
Protection Plan Protect Your Purchase
Checking for protection plans...

Recently Viewed

Features

  • 3.00-inch mandrel bent 16-gauge 409 stainless steel tubing maximizes exhaust flow and improves durability
  • A 3.00-inch polished stainless steel tips add a custom look
  • No Drone
  • Includes complete hardware and factory styled hangers in the stock locations for an easy installation
  • Delta Flow Technology Increases Performance and Reduces Drone
  • Delta Flow Technology Increases Performance
  • Backed by Flowmaster's Lifetime Limited Warranty

Description

Flowmaster 818121 American Thunder Axle-Back Exhaust System Stainless Single Exit

Color: Multicolor


Brand: Flowmaster


Material: Plastic


Vehicle Service Type: ATV


Automotive Fit Type: Vehicle Specific Fit


Brand Name: Flowmaster


Manufacturer Part Number: 818121


Manufacturer: Flowmaster


UPC: 090127140284


Global Trade Identification Number: 84


OEM Equivalent Part Number: 818121


Model Number: 818121


Unit Count: 1.0 Count


Manufacturer Warranty Description: Warranty


Included Components: Flowmaster 818121 American Thunder Axle-Back Exhaust System Stainless Single Exit


Item Type Name: Flowmaster 818121 American Thunder Axle-Back Exhaust System Stainless Single Exit


Compatible with Vehicle Type: ATV


Automotive Fit Type: Vehicle Specific Fit


Color: Multicolor


Material Type: Plastic


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Wednesday, Jul 1

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

  • Klarna Financing
  • Affirm Pay in 4
  • Affirm Financing
  • Afterpay Financing
  • PayTomorrow Financing
  • Financing through Apple Pay
Leasing options through Acima may also be available during checkout.

Learn more about financing & leasing here.

Similar Products

Top Amazon Reviews

    • Another Great Flowmaster Product!
Im a big fan of a louder than stock exhaust, I live in whitetail deer country-and am convinced that a louder exhaust scares them away from the road. I've put Flowmaster catbacks in previous vehicles. Didn't want to affect the warranty on this new Bronco, so I just went with the muffler. Sounds good. Louder than stock, without being obnoxious to the neighbors. Easy install, quality is excellent. I did apply several more coats of hi temp paint to the unit, more because I had some on hand, than the unit actually needed it. ... show more
Reviewed in the United States on May 30, 2026 by Gary McMurtrie
    • Amazing Sound & Performance Upgrade!
I installed the Flowmaster 818121 American Thunder Axle Back Exhaust System on my Bronco and it completely transforms the drive. The exhaust tone is deep and aggressive without being obnoxious – perfect for daily driving but still fun when you get on it. The quality feels excellent with solid stainless-steel construction and a polished tip that completes the look. It was fairly easy to install using the factory hangers, and I’ve noticed better throttle response and a little extra power compared to stock. Great upgrade for anyone looking to improve sound and performance! ... show more
Reviewed in the United States on February 28, 2026 by Ahmed Effendi
    • Not their best work:-(
I've been a lifelong fan of Flowmaster. I've used them on a dozen vehicles over the years and they never disappointed...until now. Based on the various reviews, I expected something very different then what I got. There is certainly no "thunder", not even what I would call an agressive sound. When I first started it up, it sounded very much the same as stock, so I thought maybe it would sound better on the drive. Not so much! Is it a different sound, yes...but you have to really pay attention to catch the subtlety. It does sound pretty nice in sport mode, if you don't mind wrecking your gas mileage. It also has an odd resonance when you are just cruising with a steady pedal, not accelerating or slowing down. It's almost an annoying tone, one that will make me rip it off and replace it again, if I don't get used to it. All in all, would not recommend, certainly not for $550. If it wouldnt take my truck down for a week waiting for the replacement, I'd honestly send it back for a refund. ...disappointed ... show more
Reviewed in the United States on May 7, 2026 by MadMachinist
    • Sounds great, easy to install
Got it because it was high clearance and to replace the muffler delete. The muffler delete was too loud, this sounds great on the outside and is about 100x quieter on the inside. It took about 10 minutes to install.
Reviewed in the United States on March 17, 2025 by joseph vandervloedt
    • Sounds great
Great sound and quality. As others have mentioned the hangers don’t make sense and the instructions are terrible. You will need to be creative to make the hangers work.
Reviewed in the United States on December 2, 2025 by Sean Jennings
    • Good sound, bad hangers. Good sound, bad hangers.
Review Image by BEN
Review Image by BEN
Review Image by BEN
Ultimately I like this axle back kit. It tucks up nicely, sounds decent, and is about the cheapest option out there. That said, the mounts are terrible. It’s obvious what Flowmaster intended with the design and parts provided but it just didn’t line up on my truck. And I broke 3 of the 4 cheap metal clips just trying to install them on to the hangers. I ended up tapping everything to 1/2-13 and installing top lock nuts to retain the red bushings instead. Do better Flowmaster. ... show more
Reviewed in the United States on June 23, 2023 Reviewed in the United States on June 23, 2023 by BEN
    • Loud!
Sounds great and loud when on gas, but still quite when cruising around
Reviewed in the United States on August 18, 2025 by Glen Mead
    • Great sound
Not too loud. Easy to install. Slight modification to the bracket to fit my 2023 bronco. Does not hang low like the stock muffler.
Reviewed in the United States on May 17, 2023 by T

Can't find a product?

Find it on Amazon first, then paste the link below.
Checking for best price...