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Your cart is empty.Flow master 817669 American Thunder 409S Cat-Back System with Aggressive Sound
Customer
2025-09-03 12:10:09
Perfect fit. Took about 2.5 hours to install. I wamt to address several questions i had tgat were not covered in other reviews.The clamps are terrible as many other reviews have stated. I fixed this by disassembling the clamps and putting the clamp in a vise and using a punch drifting out the bolt from the wedge shaped piece that prevents the clamp from tightening all the way. Discard the wedge.Using a cordless impact wrench these tightened down perfectly.Also don't do what I did....the star washers are used last to hold the new exhaust flanges to the rubber mounts. They go on last and are NOT used on the one mounting flange that you will bolt on the left (drivers side) of the vehicle. I ruined two of them with this as they are shipped all on the bolt and you think they go on the bolt but they don't.I was a lityle worried about how loud it would be. I'm glad I did nor get the American Outlaw. The American Thunder is perfect! Nice classic rumble. It does drone while towing a bit when under 2000 RPM. At 1800 RPM there is a really loud drone.The V4 issue is a little different of a tone, more of a warble than anything. I don't find it to be an issue.I was also worried about rear exit and the sound bouncing off my camper when towing and being annoying in the cab. I'm pleased to report that this is a nonissue
Dardwa
2025-07-23 11:17:40
Tail pipes look great, and added horsepower too! Not loud but will definitely get louder as time goes by.
Brandon C. Darke
2025-07-11 16:16:59
I purchased this exhaust for my 2014 Silverado LTZ Z71 Crew Cab 5.3L gas truck. Start to finish it took 2.5 hours to remove the OEM exhaust and install the new Flowmaster. I installed it with a 3/8†drive ratchet, 10, 13 and 15 mm deep well sockets. A hack saw was used to cut behind the original muffler for removal of the Tail pipe section. No pneumatic or electric tools were used. I did need to use a cheater bar to supply sufficient torque to tighten the clamps. The sound is great. Start-up of the vehicle delivers a good rumble to let you know the exhaust is there! When the engine is idle the exhaust is very tame. Putting the truck in gear and hitting the gas delivers that great Flowmaster sound one would expect from there proven exhausts. The low RPM sound is amazing, delivering a very deep rumble that will turn heads. As you accelerate through the RPMs the sound of the exhaust gets more of a higher pitch sound but still rumbles with great presence. The deep rumble returns with the shifting of each gear in the automatic transmission. While cruising at any speed that the computer deems necessary to switch to V4 Mode, the exhaust exhibits a drone that is not annoying after the second time you hear it. The drone usually doesn’t last long as the truck with any form of road incline automatically switches to V8 Mode and returns to the great Flowmaster sound. There was no additional cutting or welding needed. Though the clamps are probably sufficient enough to last a life time (heavy duty), spending the extra money to have the exhaust welded up would probably be the safest bet. I plan to have it welded up soon.
Chillinorange
2025-06-30 17:53:25
Great sounding system and easy to install. I have a 3" leveling kit with 33" tires and didn't need to use a lift or jack. Clamps are a little tricky as they don't tighten unless they are right at the end of the pipe near notches. I still put a couple of spot welds just to make sure everything stays put.I got the order from Apexracing and the first box was missing the instructions, muffler, and 1 chrome tip. Apex was great in getting the problem fixed right away. Their customer service was top notch.
airspazz
2025-06-27 13:32:04
I purposely bought a direct fit exhaust kit so I could install it myself with out welding it. The tail pipes are either not bent right or the hangers are not in the right places. The tail pipes also do not fit together properly either the joints are over expanded so the pipes do not fit tightly together so when you tight the band clamps the pipes are still loose and move. The exhaust tips do not fit right either. This is way over priced. For what I got. I had to go out a buy two stainless clamps because two of the band clamps stripped out.
Jeff
2025-06-19 12:57:51
Product is great, easy install, sounds great but the box was just about wrecked one pipe dented and package taping all over. Somewhere in the delivery process or at the warehouse, it was opened and the exhaust tips were stolen. Flowmaster aka Holley Inc. Customer service was awesome and they comped me the tips which arrived 3 days later. Whoever stole the tips could suck it.
AL
2025-04-14 17:05:15
Flowmaster has always made the best exhaust systems imo. And with the American Thunder they haven't disappointed! If you want a TRUE old school muscle sound then this is the exhaust for you. Installed on my 2018 Chevy Silverado 5.3 reminds me of my muscle cars back in the 80s. Unlike a muffler delete, this system has a very CLEAN, deep tone that you can feel and hear. For those saying it's quiet, I would suspect they are not actually running this system. Early morning start ups are enjoyed by my neighbors too. Driving through town, heads turn constantly and you will be checked out closely by other muscle cars and trucks. I chose to go straight out the back and I can hear it in cab which I like, but not overly loud as to not be able to speak with your passenger, though the sound is there. If you want quiet, this system is not for you. If you want a loud deep rumble but not obnoxious then you have found the right system! Very fast shipping, hardware was all there and is good quality. I did have ONE con and that was one of the welds on one of the tips let go. The reason I did not remove a star for this is because I contacted Amazon about it and they are shipping me out a new tip. They made things right immediately, so I have no reason to remove a star! Warning though, you will not be able to go under a bridge without getting on it, but hey, that's all part of the fun!! Thanks Flowmaster
Kevin Davidson
2025-04-06 10:07:00
sound is perfect for me not too loud not too quiet very pleased
Alexandre Boileau
2025-03-07 13:00:05
Deep growling sound. I'm impressed. Installation is pretty easy. The look is amazing. I recommend this product.
adam
2025-02-06 13:07:04
Sounds nice on my 2014 silverado
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