(approx) 1 Hour
Simple installation for anyone.
I’m Justin with AmericanMuscle.com and I’m taking a closer look at Flowmaster’s American Thunder Classic Axle-back exhaust for the 2005-2010 Mustang GT. The classic incorporates the tried and true 40 series muffler, which is the muffler that started it all for Flowmaster many years ago. Now this sound defined Flowmaster and is one of the more aggressive exhausts you can get from their lineup. The classic just like the standard American Thunder incorporates that same 16-gauge aluminized steel for its ability to resist corrosion and its overall durability. Now just like the American Thunder standard, the classic also features that very cool black finish for a stealthy look, however features a slightly larger 4” stainless tip embossed with that very cool Flowmaster logo. Getting the classic bolted up to your Mustang is a very straightforward task, and should take you only about an hour using basic hand tools. Now let’s hear how Flowmaster’s American Thunder Classic sounds compared to your factory exhaust.
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Features, Description, Reviews, Q&A, Specs & Installation
Technical Note. Americanmuscle recommends adding the 2005+ Mustang 304 Stainless Steel Exhaust Hanger Kit from the drop down option above, to provide more strength, stability and a cleaner installed appearance. If you have a 2007 Mustang you may need the kit for correct installation.
Fitment: 2005 2006 2007 2008 2009 2010 Details
CA Residents: WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov
March 07, 2020
2008 GT 4.6 3Valve
Minor cabin noise/buzz/moan around 1800-2000 rpm (60-65 MPH) in 5th gear (stick shift w/ 3.55 gears) while climbing hills, otherwise exactly what I was looking for.Helpful (0)
September 28, 2019
Powerful sound. Great purchase. It took about three hours to install. I recommend.Helpful (0)
February 19, 2019
Quality has really gone downhill
I remember when flowmaster products were deep, throaty and great sounding. This seems to be a thing of the past. These drone horribly between 1800-2000 rpm. They are only reasonably quiet at idle. They fitment wasn’t even close. I tried my best to get them straight, but ultimately had the local muffler shop cut and weld them into place. His quote was “how can a reputable company sell garage like this”. I’m putting my Roush extreme tailpipes back on after work today. No knocks on AM, but flowmaster has really been a complete disappointmentHelpful (3)
July 24, 2018
Old school. Sound
Nice. Sound. For. My. 2008. Mustang. Gt. Reminds. Of. 1967. Mustang. S. Code. Installed. In. One. Hour.Helpful (3)
June 18, 2018
This is my second set of these mufflers. We just bought a 2010 Mustang for my wife and the first thing she had to have were Flowmasters.Helpful (4)
December 27, 2017
Flowmaster American Thunder
I installed this exhaust on my 2010 Shelby GT500. On opening the box, I noticed that one of the tips was welded on slight off center. This was the second Flowmaster kit I purchased with this issue (first kit NOT purchased through American Muscle). I did not return it to American Muscle because, A- not their fault, B- it was not crazy crooked as the first kit was, C- I wanted this exhaust. Installed easy after jacking up back of car and I had to remove both brackets on each muffler to install. On MY car, the Flowmaster tips did not come out as far as stock. My main issue is that the DRONE between 1600ish and 2000 rpm is ridiculous!! Vibrates bit in the car. As my car runs at 1750 rpm at 80 mph, it’s kinda ( read Really Really) loud and distracting. Not figuring in the drone, the exhaust sounds AMAZING during start-up, idle and under acceleration. Tips look great, wish they stuck out another 2 inches. If I could go back in time, I would try the next quieter exhaust kit. I would still stick with Flowmaster, without a doubt.Helpful (3)
November 17, 2017
Sounds like I wanted it too. A little loud for the wife. But I love it.Helpful (3)
September 21, 2017
Very nice sound... some drone, but awesome. Very easy to install.Helpful (3)
August 23, 2017
One of the best sounding mufflers on the market!!! The install was simple. I have Kooks long tube headers with Kooks catted x-pipe and the car sounds amazing with the Flowmaster mufflers!!! I have had many different mufflers on my GT500 and none sound as good as the Flowmaster American Thunder!!!Helpful (4)
June 01, 2017
Good deep sound. Waiting for mufflers to burn out a little and get louder.Helpful (4)
The American Thunder will be more in the middle in terms of how loud they are. They will be quieter than the Outlaws, but louder than the factory exhaust. I'd say it's about a 5 or 6 out of 10.
Will they fit with long tube headers and an x pipe? If not then what full exhaust system do you recommend for a 05 mustang gt.
These would fit with long tube headers and an x-pipe but you would need over axle pipes as well to ensure a good fit. We usually recommend cat-back systems for long tube headers and x-pipe modifications to get the most out of your system. We do have the American Thunders in a cat-back system by Flowmaster here: https://www.americanmuscle.com/flowmaster-american-catback-0510gt.html.
Have stock 07 GT, with Flowmaster Force II kit on it. How does this American Thunder kit compare to Force II Ford Racing FR500s? Want a little more V8 sound, but don't want one that's very loud and annoying to everyone else on the road. Seems like most kits are either too quiet or way too loud. Is there a kit in the middle? Thks!
The Flowmaster American Thunder Axle-Back Exhaust will be louder and more aggressive than the Flowmaster Force II and just slightly less aggressive and loud than the FR500S exhaust. The Flowmaster Force II will be the deepest most "muscle car" of the three.
Does this exhaust fit with the Roush Rear Valance
The Flowmaster American Thunder Axle-Back Exhaust is designed to git the 05-10 GT Mustang. The Roush rear valance utilizes a square cut out for squared tips.
what if you have 3" exhaust coming from headers, do they come in 3" or just 2 a half inch?
If your exhaust is 3" but the axle-back exhaust is 2.5" you will need to have it clamped down properly. However I would suggest purchasing an exhaust where the pipe size is 3" because you can be subjected to exhaust leaks or back pressure.
Yes it sure does!
You really will not see any gain in horsepower with any axleback setup. There is not enough back pressure built up at that point in the exhaust to affect your performance. Axle back exhausts are strictly for sound purposes. For performance you will want to look into headers and a mid pipe.
It might take a little hammering and bending but as long as the pipe diameters match up, then you should be fine. You might also have to hang your own brackets for the exhaust hangers though.
(approx) 1 Hour
Simple installation for anyone.
What's in the Box
|Piping Material:||Stainless Steel||Tip Material :||Polished Stainless Steel|
|Piping Size:||2.5"||Tip Size:||4"|
|Muffler Type:||Chambered||Fitment:||2005-2010 GT, Bullitt & GT500|