Flowmaster 818121 American Thunder Axle-Back Exhaust System Stainless Single Exit
Condition: New
$549.92
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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.
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Availability:
20 left in stock
Arrives
Saturday, Nov 7
At a glance
- Condition
- New
- Color
- Multicolor
- Material
- Plastic
- Vehicle Service Type
- ATV
- Finish Type
- Stainless Steel
- Automotive Fit Type
- Vehicle Specific Fit
- In the box
- Flowmaster 818121 American Thunder Axle-Back Exhaust System Stainless Single Exit
Features 7
- 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
Specs 19
| Color | Multicolor |
|---|---|
| Brand | Flowmaster |
| Material | Plastic |
| Vehicle Service Type | ATV |
| Finish Type | Stainless Steel |
| Brand Name | Flowmaster |
| Manufacturer Part Number | 818121 |
| Number of Items | 1 |
| Manufacturer | Flowmaster |
| UPC | 090127140284 |
| Global Trade Identification Number | 84 |
| OEM Equivalent Part Number | 818121 |
| Item Type Name | Flowmaster 818121 American Thunder Axle-Back Exhaust System Stainless Single Exit |
| Model Number | 818121 |
| Unit Count | 1 Count |
| Manufacturer Warranty Description | Warranty |
| Compatible with Vehicle Type | ATV |
| Automotive Fit Type | Vehicle Specific Fit |
| Material Type | Plastic |
No specs match.
Frequently asked questions
If you place your order now, the estimated arrival date for this product is:
Saturday, Nov 7
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.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
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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.
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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!
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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
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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.
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.
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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