rnail

So after obscessing over this and listening to different sound clips, it has come to my attention that the manual and auto versions of the stock mufflers are different. What is the difference? The aftermarket replacements seem to fit regardless. Are the manuals louder or tuned for a different RPM range?

I'll be making my decision soon Flows or FRPP GTAs.

To anyone with the stock H-pipe and GTAs, I would love to hear a sound clip.
Thanks for the help.

red454

I believe the auto mufflers are tuned differently due to the shift points of the auto transmission - and if I remember correctly, the manual mufflers are a little louder.

I know that there are different part numbers (and costs) for the auto and manual mufflers.

I have modified my stock mufflers so I know what they look like on the inside, but I have not seen the inside of a muffler from an auto equipped car.

rnail

That is a really cool cutout of the muffler - nice job. Looks like a combo of what is found in a Dynomax super turbo and a chamber for deadening. Someone really thought about this to get the flow and sound for the stock system.

neil07gt

since these don't appear to be glass mufflers, unless i'm missing it in the pic. i'm puzzled why some people say their mufflers get deeper as time goes by.

red454

If you look in the picture you will see a bulge in the exhaust pipe, right before it exits the muffler and connects to the stainless tip. That is actually a double wall area and there is fiberglass packed between the walls.

One of the modifications involved cutting an opening into that pipe, as you can see in this picture. The two walls or layers are visible. There was not much fiberglass, but it was definitely sandwiched in there...

What I did in addition to opening the main pipe was to add a second tube into the resonating chamber. You can see the small tube (1.5 inch diam.) in the pic - I opened a hole into the divider wall and added a 2.5 inch dia. pipe next to the current one. Unfortunately I did not get any pics of the second modification before I welded the covers on.

The mods give the mufflers a deeper, more aggressive tone, with almost no drone.

Glenn

do you think if you would have cut a smaller hole in the pipe, there would be no drone at all? At what rmp do you hear the drone. I like your idea alot.
Maybe an x-pipe and a little chop chop is all I need. Thanks

red454

Well, the drone (in my opinion) is really very minimal. I doubt that most people would even notice it - and I am very picky about the sound.

After I cut the top (cover) of the mufflers, I made new covers and tie-wrapped them in place. Since my plan was to experiment with the internals, it would be easy to cut the tie wraps to gain access, make whatever changes, and then put the covers back on for a test run.

But even with the covers securly tie wrapped, there was a lot of drone. It would rattle your back teeth. So when I finally got a sound that I liked (my wife thought it was way too loud) I welded the covers on. But what I did not realize was how much sound was really coming from the 'loose' covers. With the covers finally welded in place, the mufflers were so quiet that it was hard to tell them from stock. I was disappointed.

The last change I did was to put a cover plate over the rectangular hole that I had originally cut into the main pipe. I did that because they were just a little too loud. I opened the mufflers up again and opened a hole back into the main pipe. I then had to make some new covers, and closed the mufflers up.

So, now they are a little louder than stock. Deeper. But exhaust sound is so subjective. You really have to hear them. The videos that people post sound good, but anyone with a modified or aftermarket system will tell you that you really have to hear it in person to get the full effect.

Now all I have in these is my time and $20 to buy a second set of stock mufflers. I figured that if I ruined them, I would not be out much. But if I got a sound that I liked, it would really be a one-of-a-kind.

Glenn

has any one cut open an auto muffler yet??

metroplex

You could just check to see if the auto mufflers have the same part #s as the manual mufflers.

2Slack

They have different numbers from what I remember.

SteelTownStang

I see that you must have a lot of time on your hands. I don't think that I'd go through that much trouble, but kudos for the effort .

aircare84

The manual mufflers have a 'GOG' tag on them, not sure what the autos have.

theedge67

Autos have "AOA" tagged on them.

SteelTownStang

Yes, When I removed mine, they still had the chalk/marker hand writing on them...

metroplex

The auto mufflers are $120 and the manual mufflers are about $160 each, so yes you guys are correct. There is a difference in the mufflers!

FWIW I had to spend a lot of time and money to make my Crown Vic exhaust sound almost as good as the stock exhaust on the manual GT.

GPStang06

Hmmm this is interesting. When I had the Magnaflow High Flow X installed I was afraid it would increase the drone by a lot. My friend has it but with Steeda Axle backs and his drone is far worse then mine. To my suprise mine is no where near his and infact sounds a little less (the drone, stinger sound is louder which I like). The only difference between us is he has an automatic. I guess since he can't drive around the drone with the auto it appears much worse.

metroplex

He could tune his shift schedule to avoid prolonged driving in the 1800-2000 RPM range.

Glenn

well I just put my ebay gog mufflers on with the Red 454 mod done to them. I cut my pipe hole about half the size he did for fear of being to loud. I like the sound of my car a lot more now.
I got my mufflers for 50 bucks delivered to the door.
SteelTownStang its what real car guys do! We don't care about the effort or the time. I enjoy working on my car and if I can get the sound I want and save a few bucks in the process ... all the better.

SteelTownStang

Kudos to you too Glenn. You real car guy

red454

So, how much of a difference did you notice?