I recently (several months ago) bought a 1997 F-150 Standard Cab with the 5.4L and an aftermarket exhaust. I don't know the specific type of exhaust but it's from the cat back.

I notice that at highway speeds (55-60 miles per hour) there is an annoying resonance in the cabin. Above or below that speed range the resonance disappears.

Any suggestions on how to tune the exhaust to eliminate the resonance? I am open to messing with it a little but don't want to pull out the cutting torch.

Could it be possible to solve this problem by doing something with the intake? I have the stock intake.

Thanks.

 

Nope, the only thing that's going to change that involve way more work than just buying a larger muffler (like the Magnaflow setup) to quiet it down.

An intake won't change the resonance of the exhaust enough to matter.

 

I agree with SRockwood, the intake isn't the problem. Not that the intake wouldn't change the tone/sound of the exhaust though. The problem is simply the cat back system. If the system is still in good condition you can swap out the muffler with a quieter one, but if the system is reaching the end of it's life you'd be better off swapping out the entire system. I'd recommend the Flowmaster Cat-Back system. It has a very nice mellow sound with no resonance and exellent quaility for the $$.