I installed a cat back Flowmaster super 10 a couple weeks ago. Single in, single out, no resonator delete. Just cut out the Ford muffler and installed the Flowmaster.
The super 10 sounds great not really disgusting loud, defiantly has interior resonance however....
But the real problem is when the truck is pushed to high RPM. (I floor it) The exhaust gives off a strange high pitch humming noise. Similar to what a super charger or turbo would sound like.
This is just a 2018 XLT V8 5.0, no super charger.
This started occurring right after the muffler change.
Has anyone else experienced this, and if so have you found a way to remedy the phenomena?
This was not occurring with the stock muffler.

 

A "cat-back" exhaust is literally everything after the cat. It sounds more like you just cut the stock muffler out and welded the super 10 in. I did the same with a Borla S-Type muffler and I found it to sound perfect (i.e. no weird sounds).

 

Yes, thats why I said in the post I just cut out the Ford muffler and installed the Flowmaster. I am saying I did nothing but replace the muffler.

 

The problem is running a chambered/baffled muffler without any packing. You're going to get some interior resonance with it unfortunately. My recommendation would be to find a muffler with a similar tone and sound and swap to it

 

the high pitch sound you are hearing is probably the exhaust tip....do you have a dual exit tip? Mine did this as the tip i put on is dual, it will scream at 5k rpms....i hate it, but to lazy to fix it. It also could be a bad weld or if the way the piping lays together.

 

Its a single tip exhaust. Same pipes that where on the stock muffler. Just had to add a little extra pipe because the Flowmaster 10 is a fraction of the size of the stock Ford muffler.

 

I noticed today that my noise occurs at the same area. Right around the 5k rpm range