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Discussion Starter #1
I know you can put a car up on the jacks and spin the pinion 1 revolution and measure distance the wheel rolls to determine gear ration. I'm a shade tree mechanic you know. Anyway, how can you tell the difference between an 8 3/4" rearend and a 9" rearend? I think I got two lockerboxes but not sure. Also I've heard of limited slip and Posi rear ends, but is there such a thing as a semi posi in the '71 to '73 cars?
 

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Geez, now you've got me thinking about Marissa Tomei's rear end. Hmmmm...... Limited slip and "posi" are the same thing. So is TractionLoc which was Ford's name for a limited slip rear end. "Posi" is just a contraction of Chevy's limited slip identifier - Positraction. As far as 8 3/4" and 9" rear ends and telling them apart, I can't help you. First generation Mustangs had either 8" or 9" rear ends depending on how they were powered. Higher performance and big block models had the beefier 9" units. Most of the grocery getters had 8" rear ends. 351W's and 351C's had nines. Most 289's, 302's and sixes had eights. Of course, a PO can change all that after the fact(ory). The usual identifier of a 9" is that you can't get a socket directly up on the two lower case bolts that hold the pumpkin into the third member. The bolts on the eight inch rears are accessible. Also, the 9" is fairly round in shape while the 8" looks slightly rectangular.
 

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Discussion Starter #3
"I see" said the blind man as picked up his hammer and chisel to go look. I just got a '73 with a 302 in it. Probably an 8". Which is bigger than mine but smaller then the Boss with the 351C 4V. It's my grocery getter.
 

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Discussion Starter #5
I had to go look. The '73's got a standard 8" and the '71's got a standard 9" just what you would expect. Thanks for your help.
 

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You have to see the movie "my uncle Vinnie" to get it.
 

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The movie is actually called "MY COUSIN VINNY". Right?!
 
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