1972 Rear End and Exhaust Mufflers

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sr71kadena

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How is the best way to tell if you have an eight- or nine-inch rear end? I do know that I have 31 spline axles. I just bought my Hooker Headers and wanted to get any recommendations on best sounding mufflers. I am rebuilding the 351C with CNC heads with an aggressive Comps Cam. Thank you in advance. I'll upload some pictures later.
 

canadian_red_maple_leaf

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1966 Mustang K-Code Coupe
1968 VW Beetle
1969 Mustang Mach1
1971 Mustang 351 Boss
1972 Mustang Convertible
1983 Mercedes 280SL
Post pictures of the third member und of the axle ends without the drums.

That should clarify a few things

Abudi
 

timachone

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That's a typical 9 inch with the bump on the left rear of the center section
 

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turtle5353

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Tim is correct. 9” has the bump. 8” is smooth, no bump.
 
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IF it's the original axle, it should be a 9" That said, people do weird stuff over the years and it could have been swapped out for an 8"
As for mufflers, I recently installed Flowmaster FX and I like the sound. These do not drone nearly as much as the earlier Flowmaster 40's I had on before. They are made in different pipe bore sizes. Mine are 2 1/4", but I suspect you'll want 2 1/2". I'm not sure about 3" in these.
 
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Some other Fords
.... I just bought my Hooker Headers and wanted to get any recommendations on best sounding mufflers. I am rebuilding the 351C with CNC heads with an aggressive Comps Cam. ...

Re your muffler question- there are opinions all over the board on what the "best sounding mufflers" are. What might be music to one is obnoxious noise to others.

What are you looking for sound wise? Got a sound clip or a YouTube link of something you like?

For me, I wanted something just a tad more aggressive than stock. I went for the generic "Turbo" muffler sold by Precision Exhaust. It is quiet when cruising, no drone, but makes a little more sound when I stomp on it. It won't wake the neighbors but the car right next to me will hear it.
 

Hemikiller

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If you are positive you have 31 spline axles, then you'll have a 9". All 351 and better 71-73s came with a 9". The common test is if you can put a deepwell socket with an extension on the lower two nuts that attach the pumpkin to the axle housing. If you can, it's an 8", if not it's a 9", as the pinion support sits lower as shown in timachone's pic. Also, the snubber bracket on the pinion support is a 9" only part. The one for the 8" was bolted to the floorpan.

Mufflers are like asking which oil to run. My go-to muffler for a cruiser is the Dynomax Super Turbo. Doesn't drone and makes some noise when you step on it. The Hooker AeroChamber is a good one too, definitely louder than the Super Turbo.
 
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