I've had Flowmasters on all my previous trucks and with my current new exhaust setup on my 78 f150 with 351m. They've all seemed like a good quality muffler with great sound. I got dual Super 40s (2.5'' center in and center out mufflers). It's not really a new setup anymore, as it's been on the truck for about 4 months now. As little as after 2 months since the new setup, one of the flows started rattling at idle sometimes, when the truck is off and shutting the door. Nothing is loose in the system as far as hangers or anything, and the sound isn't coming from anything else. It is certainly coming from inside the muffler. I've heard of baffles inside the flows breaking off at the welds which then rattles. I bought the mufflers brand new from en ebay auction. Looks like I'm going to have to remove this one and weld in another replacement. I still like the flowmaster's unique sound and maybe this muffler was just a defect but if this type of quality is what flowmaster is going to, I will be going to a dynomax or magnaflow. Anyone else have this problem?

 

Never had a problem with Flowmasters, and they've been on several vehicles in my family. I'd say it's just a lemon sort of thing.

You sure you don't have maybe a heat shield on a cat loose? One of the welds on one of mine broke, drove me up a wall until I figured out what it was, just broke the whole sheild off, too bad of a place to try and weld it back.

 

I've got a rattle somewhere in my exhaust now too and i'm thinking that it maybe the flowmaster muffler. I've put new hangers on taken one cat out and gutted the other. Still my truck rattles at idle and i cannot find it anywhere. I really like the sound of the flowmaster but i may go to dynomax or put a glasspack in.

 

Yea unfortunately it's definetly the muffler. I have no cats on this 78' and there are no heat shields. You can actually tap the bad muffler with your hand and it rattles.

 

Don't be surprised when you go to a muffler shop that sell Flowmasters and they tell you that you have a cheapo knock off. The ends crack out of the case, guts break loose inside and Flowmaster will not touch said knock offs.
Buyer beware.
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The ones I've owned never gave problems. I ran a sido 40 series flowmaster for over 200,000 miles on my last truck. I've had a set of 40 series 2.5 in & out on my truck for 7 yrs. I have seen the knockoffs mentioned above.They look just like the flows but they don't last. I may be wrong but I think Flowmasters are lifetime warrentied. I'd check their website.

 

I know mine came with a warranty, but I'm not sure how long it was.

 

I have a Borla muffler with a million mile warranty, was told by Borla about my case, "this warranty card I can make 1,000 copies of on the computer". Then told me I may of found the muffler in the wreckers and trying to cash in, yup the wreckers also gave me a parts list with assembly instructions. Going on 4 months now fighting Borla as this muffler that sounds like it's full of gravel. With signs on said vehicle at Rover meets Borla isn't happy about the bad advertising i'm giving them about their faulty product. At $699 a cat back system I have convinced many members to not install a Borla system.

Bottom line is good luck on your warranty replacement as manufactures will try to wear you down until you go away, not this stubborn German! Small claims court is too easy as I get a bigger personal satisfaction knowing they know i'm doing bad advertising of their failed product. Off subject Flowmaster is manufactured 45 miles from me, I have had many different models of almost new Flows given to me from a friend who owns a muffler shop. Told to test and not return them hence the garbage can gets feed.

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I'm thinking the guy who started this thread got a knockoff from a muffler shop wanting to make some extra cash. Wouldn't be the first time.

 

I believe your correct on those phony muffler.
My muffler shop friend has had drive ins with those phony Flows that failed then he'll show them a real one, should see their face as they've been had.



What I just found on Borla's;

Borla stated that they can sell me a replacement muffler only not cat back for $274, heck I just found the same Borla muffler for $191.99. They will do anything to not back up their lifetime warranty then also try to rip you off with their $274 special vs $191.99. Is this how to run a business?
I know I can keep showing people my business of letting them hear that Borla 1,000,000 mile rattle and purple case spots where somethings falling apart inside.
Gots to go pack, Las Vegas plane leaves in 6 hours, nap time.

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