I have a 50series flowmaster on a 5.0 '91 F150, converted to 3" all the way back. At certain rpm's the inside cab resonance is very annoying. I'm thinking about just going back to stock , backpressure would still be low due to the 3" pipe. But can't find a 3" stock round style truck muffler. Would a resonator in front of this mufler help the noise? (front cat gutted, second cat removed). Any help/advise would be appreciated.....or anyone know of web sites that carries just truck mufflers???

 

The stock muffler is fairly restrictive. I think you'd be much better off to put in a high-flow cat.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Sunroof, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Then theres:
99' Mustang GT 4.6L
88' F-250 Superduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Top speed is 65mph, Go Baby Go!

 

A 70 series Flowmaster is supposed to be their quietest and I would think should work for you. Also, you should call and talk to a tech person at Flowmaster about the resonance. They may be able to suggest something that would help. I am thinking that maybe a smaller diameter, say 2.5-inch, pipe may be quieter and likely would not be restrictive as stock is probably 2.25 or less.

 

Did you put the heatsheid on that came with the 50 series mufffler? That will reduce interior resonance.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Sunroof, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Then theres:
99' Mustang GT 4.6L
88' F-250 Superduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Top speed is 65mph, Go Baby Go!

 

What heat shield? I never got a heat shield with my Flowmaster 50 series.

I wouldn't replace your 50 series with the stock muffler, replace it with a 70 series or some sound damping material if it's too loud.

 

I got a heat sheild that came with my american thunder kit. Says it reduces interior resonance so i never put it on.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Sunroof, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Then theres:
99' Mustang GT 4.6L
88' F-250 Superduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Top speed is 65mph, Go Baby Go!

 

Mustang GT221: I have to agree that the cat does have some sound dampening ability. The person at the shop told me that it would be louder after guting the front cat. The prob. is I have to buy the complete front cat/pipes assembly , it prob. has a nice price tag. I may call Summit and see if they carry this , w/a high flow cat.
I don't know about any heat shield........ thanks posters...
Fords forever!!! tidbit of info: don't touch that sector adjuster(power steering models) unless one knows exactly how to adjust and goes by the procedure!! I spent almost all day Sat. replacing the gearbox in the wife's Grand Marqius....because I had over adjusted it....

 

I started my truck up before i put the muffler on, the pipes stopped right out of the second cat and it wasn't that that loud at all. I was very suprised how much those two cats reduce sound. The first is just a primary and the 2nd is the big dog.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster American Thunder Exhaust, Sunroof, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Then theres:
99' Mustang GT 4.6L
88' F-250 Superduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Top speed is 65mph, Go Baby Go!

 

If you do go another route and decide to sell the flowmaster let me know how much you want. rscotth@att.net

 

I got to looking at where the muffler was located, and its right under the floorboard area of the extended cab. It should be further back. Looks like the orginal muff. was about where the bed starts, so I believe this is part of my problem of interior noise. May have it moved back here shortly. I can't find a 3" in & out stock round truck style muffler. Someone told me that the further back the muffler is, the quieter it will be. Makes sense.......

 

The back of the muffler should be connected to the dual hangers before the pipe goes over the axle. It sounds like it is in the right spot. I didn't use my heat-shield and don't want it. If you want it and want to give it a try e-mail me, GreenThunder2195(No Email Addresses In Posts!).


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster American Thunder Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

Check out my Gallery for a look-see.


Then theres:
99' Mustang GT 4.6L
88' F-250 Superduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Top speed is 65mph, Go Baby Go!