Flowmaster 17421 American Thunder Axle-Back Exhaust Kit 2.5 Inch Aluminized Steel 4 Inch Polished 304 Stainless Steel Tips Compatible with 2005-2009 Ford Mustang 4.0L V6 Coupe or Convertible
Condition: New
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Availability:
Only 2 left in stock, order soon!
Arrives
Feb 4 – Feb 7
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Features
- Includes Hangers and Hardware for an Easy Installation
- Mandrel bent 16-gauge Aluminized Steel Tubing
- Moderately Aggressive Exterior Exhaust Tone
- Dyno Tuned for Maximum Performance
- 4.00-inch Polished Stainless Steel Tip
Description
Flow master 17421 Axle-back System - Single Rear Exit - American Thunder - Moderate Sound
Manufacturer: Flowmaster
Brand: Flowmaster
Model: 17421
Item Weight: 17.65 pounds
Product Dimensions: 20.1 x 12.5 x 10 inches
Item model number: 17421
Is Discontinued By Manufacturer: No
Exterior: Painted
Manufacturer Part Number: 17421
OEM Part Number: 17421
Date First Available: October 10, 2006
Frequently asked questions
If you place your order now, the estimated arrival date for this product is:
Feb 4 – Feb 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
Style: Base Product
Installation wasn't hard at all, getting the old muffler out was harder. Here's a quick guide, since I couldn't find any good videos on removing the factory. There are two hangers that support the factory muffler, as well as some sort of rubber band on the back. The hangers came out pretty easily (13mm bolts, ratchet worked with most of them but I needed a wrench for one just due to the position). The rubber band hanger thing wouldn't detach and wasn't really important anyway, so I just cut it off. Getting the muffler off of the car's exhaust pipe was the hardest part. There's a little nub that fits into a cut in the factory (and flowmaster) muffler. Douse the entire connection with as much WD-40 as you can find, then twist that sucker back and forth while pulling it forward and down. If all else fails, whack the connection with a hammer a couple times to loosen up the joint. Whack the ring on the connection a few times too, but mine was welded onto the factory muffler. Once the old rusty factory one is off, grab your shiny new Flowmaster, put the included clamp ring around the not-shiny end, and shove that thing over the factory pipe. Remember that nub- you'll have to fit the little cutout around it. Once it's all the way on, move the ring to right around the nub (Mine is maybe 5mm before the cutout for it) and tighten it down pretty much all the way. That's solid steel, so it'll hold up the muffler well enough so you dont have to hold up 15 pounds of steel while trying to bolt stuff on. Then slide the two muffler hangers around the pegs on the top (and just ignore the peg at the back, that's where the rubber thing would connect but it really doesnt matter) and start bolting it up. Make sure you've got the tip in the right spot before securing it down. Once everything is in place, get all that stuff nice and tight, start up your stang, and enjoy that beautiful sound. It'll smell like burning plastic for the next little while since there's some junk inside of it that might melt, no biggie. Review-wise, I absolutely love this muffler. Sounds amazing, but not loud. I honestly think it sounds better than a stock GT. It's not annoyingly loud, and at moderate radio volume I can't notice the exhaust at all, but when I hit the gas it sounds AWESOME. This is also the cheapest I can find it anywhere ($270 on AM and other sites, I got it for $220 on Amazon) so just buy this. The Pypes just makes a lawnmower sound, this is absolutely worth the extra money!
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Reviewed in the United States on August 15, 2018 by Grant Fowler
Style: Base Product
sounds great...install was super easy....waaaaay overpriced for what it is
Reviewed in the United States on May 21, 2025 by Kirt J.
Style: Base Product
I bought this axel back system because I was never happy with the sound from my V6. I had previously tried a GT Take Off Muffler (an exhaust removed from a new GT) and while it sounded a little better than stock it was simply not good enough. I just fitted this Flowmaster in under 45 minutes and went for a 10 minute test drive. Yes it is that easy to install this on a 2007. The sound is great, much deeper than before, louder but not too obnoxious. No drone on the highway but a great sound everywhere else. I would highly recommend this exhaust. No it wont sound like a V8 but it certainly sounds more muscular as it should, and there is a definite performance improvement. Overall I am very happy with this purchase. I had considered going to true dual exhausts but in the end the cost just for an improved sound, didnt make sense. One last thing to mention, the exhaust has been on the car for a week and it sounds better than when it was first installed and there is a definite performance improvement. Flowmaster claim 10 HP and I can certainly believe that.
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Reviewed in the United States on November 17, 2010 by David Moore
Style: Base Product
Hangers are spaced so that the can of the muffler hits subframe under trunk area when you hit a bump. Makes a thonk noise that drove me crazy so I had to uninstall
Reviewed in the United States on June 26, 2019 by tim n.
Style: Base Product
Came dented as in pic's, the hangers are to short banged against the frame, the pipe that came out was up against the plastic bumper melted the top and blistered the paint. no adjustment. Had to take it to a muffler shop to have longer hangers and add a piece of pipe to make it fit correct, Has a loud drone at lower speeds, you would think that flowmaster would build it right for as much as they charge.
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Reviewed in the United States on January 16, 2020 by rooster rooster
Style: Base Product
I installed this on my 05 convertible and what a difference over the stock muffler. The sound is very impressive on acceleration and has a nice deep growl to it when idling. The install took about 2 hours only because the previous owner had the bolt connecting the stock muffler to the pipe welded on. A sawzall took care of that pretty quickly. After that it was just a matter of removing a few hangers and getting the old muffler off. I had considered converting the system to a dual exhaust but this worked out just fine with much less hassle. Very good value for the money.
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Reviewed in the United States on June 28, 2017 by Chuck B.
Style: Base Product
Nice sound! Fit easily once I straightened out the connecting end and made it round again. It arrived dented in, probably due to insufficient padding in the box. Had to saw a little bit off my Curt trailer hitch bracket to provide some clearance; not a heavy load carrying part, so I'm OK with that, I just tow a small inflatable boat. Sounds even better once you put 100 miles on it. It really roars when you get on the gas, but it's just a little noiser than stock around town.
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Reviewed in the United States on August 28, 2017 by Nergo Pthycc
Style: Base Product
Sounded pretty darn good for the first couple months......Now it sounds like a FART BOX!!!
Reviewed in the United States on January 12, 2016 by Hunter