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Discussion Starter #1
Does anyone know how to tell how many splines are on an axle? I've got a 67 Cougar with what I believe is an open 3.00 8" diff.

I'm just curious because I found a complete 8.8" 31 spline rear diff from a Crown Vic on CList with Posi and 3:23 gearing for 200 and a set of 3:73 gears for 150. It'd be nice to have a Posi 3:73 rear for (probably) less than 350. I thought maybe I could toss that in place of the one I have provided it will fit with most everything else. Would it work or would I need new axles or any other new parts? (I obviously don't know much about diffs or rear ends)

Any info would be much appreciated.
 

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Discussion Starter #4
In any case, how do I tell how many splines I have so I know which gear set to buy?
 

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Discussion Starter #7
One last question. Does the gear spline have to match the axle spline exactly (I assume it would)? Every gear set I've found has a 25 spline (Summit, Jegs, MustangsPlus, etc.). I'm having a hard time finding any that are 28 spline in the 8", only in the 8.8" and 9". I have founf drop-in diffs that are 28 spline but no pinion gear sets. Am I just not looking hard enough?
 

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One last question. Does the gear spline have to match the axle spline exactly (I assume it would)? Every gear set I've found has a 25 spline (Summit, Jegs, MustangsPlus, etc.). I'm having a hard time finding any that are 28 spline in the 8", only in the 8.8" and 9". I have found drop-in diffs that are 28 spline but no pinion gear sets. Am I just not looking hard enough?
I believe that the 25 spline count, is for the 8 inch pinion gear.
 

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Discussion Starter #9
Ah. So they aren't related. Good to know. I guess any 8" gear set would do then?
 

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RedCougar, while you have your learning on, if you have any other questions related to the splines themselves, feel free to ask as my company makes the splines on those shafts.
 
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