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Discussion Starter #1
What is the main benefit if any to replacing the pipe and muffler from the axle. I have seen all these sites and posts about replacing the pipe and the mufflers, why not just replace the stock mufflers with performance mufflers, and leave the piping alone. Its what I did on my trucks and the one car I had with duals. Am I losing something by just replacing the muffler?
 

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Are you talking about the pipe from the stock H-pipe that goes over the axles to the mufflers? An "axle-back" doesn't include those pipes. Only the mufflers themselves like you suggested replacing. A cat-back replaces the over-the-axle pipes and the mufflers.

Some claim replacing the over-the-axle pipes will give you a couple more horsepower because the pipes are crimped where they go over the axles. Not many dyno tests out there proving this though. Mostly changing things out after the cats is just for sound. So a lot of people do exactly what you suggested, which is just changing out the mufflers, or axle-backs, and leaving the over-the-axle pipes alone.
 

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If you just replace mufflers you dlwont have any power gains. If you replace the mid pipe and get rid of cats you will have a few more hp. 10 to 15 more.

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"axle back" means everything from the axle back which on these cars is just the mufflers -- there is a very small section of pipe attached to the muffler behind the axle, but basically it is just the muffler

"cat back" means everything from the catalytic converters (actually the mid-pipe) back, which would include some pipes and also the mufflers

benefit of "axle back" is sound and sound alone . . . some manufactures will claim that they improve flow and performance, but it is negligible

"cat back" MIGHT have some performance improvement, but the stock pipes flow pretty well, so I doubt that would be noticeable either
 

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Axlebacks are easy to do. No cutting required and they won't mess with your warranty.
 

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"axle back" means everything from the axle back which on these cars is just the mufflers -- there is a very small section of pipe attached to the muffler behind the axle, but basically it is just the muffler

"cat back" means everything from the catalytic converters (actually the mid-pipe) back, which would include some pipes and also the mufflers

benefit of "axle back" is sound and sound alone . . . some manufactures will claim that they improve flow and performance, but it is negligible

"cat back" MIGHT have some performance improvement, but the stock pipes flow pretty well, so I doubt that would be noticeable either
Not that I don't believe you, but can you provide any source on this please? I heard that cat backs (leaving stock cats alone) provide more HP, but axle-backs only provide sound, not additional HP. I am about to buy cat-backs, but if there is litterally no difference in performance of axle-back vs. cat-back, then I'd prefer to save a penny and go with axle-back.
 

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Many AB's weigh less, sometimes a lot less.
The Roush AB's drop around 25 pounds from the car.

If there is any logic in a cat back adding power becuase of crimped pipes, I don't see how going from a chambered muffler to a straight through doesnt add some power, but I can see how it won't be much.
 

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Discussion Starter #8
So lets say I simply replace my stock mufflers with some flowmaster 40 series or a borla muffler, what im hearing is that im only going to get a sound change. It doesnt help at all even being a free flowing muffler?
 

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So lets say I simply replace my stock mufflers with some flowmaster 40 series or a borla muffler, what im hearing is that im only going to get a sound change. It doesnt help at all even being a free flowing muffler?
Yep. You are correct. Even if you get 2 or 3 whp on a 3600lbs car it wont make it any faster.

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i did an axle back and a bassani x pipe.
it works well for me, and i really dont think i've left any hp on the table, by not replacing the pipes going over my axle.

if u buy an axle back, and want to make it a cat back, you can mix and match to create your best options.. ie.. Ur choice of x pipe, JPC over axle pipes, then your choice of axle backs.

just some food for thought
 
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