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Old 07-02-2014, 03:57 PM   #1
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axle splines

I have been researching options for a rear end replacement/upgrade and have found that they offer 30, 33 & 35 spline axles/spools for the 12 bolt I'm favoring. Is more splines always better? Does more splines equal bigger diameter axles or same diameter axles with smaller splines?

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Old 07-04-2014, 04:11 PM   #2
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Re: axle splines

Interesting website:

Pirate4x4.Com - Extreme Four Wheel Drive

An actual diametrical pitch specification will be a number specifying the number of teeth per inch of pitch diameter. Industry standards state that most modern automotive axle shafts (All of the 28, 30, 31, 35, 40 spline axles that interest us) are 24-pitch. Therefore, if the shaft had a 1-inch circular pitch diameter it would have exactly 24 splines (or teeth). Using this standard diametrical pitch of 24-pitch a 35-spline axle has a major diameter of 1.500 inches; a 40-spline 1.708 inches.
You have to read the formula for determining the pitch diameter from the number of splines, because that explains why a 35-spline axle has 1.500" pitch diameter splines, while it would appear that it would be 35/24 = 1.458" based on the example of a 24-spline axle having a 1.000" spline pitch diameter. Not sure how they explain that discrepancy.

But the point is, as the spline count increases, the diameter of the end of the axle carrying the splines increases. Then, while the case is made for necking the balance of the axle diameter down to slightly less than the root diameter of the splines, there is no direct correlation of the axle diameter to the spline section diameter.

copy & paste following link

That's all the theory... I have never compared the diameter of for example the various spline counts offered for the 12-bolt. But if you expect the axle to be stronger, the diameter of the splined portion has to increase, hopefully with a commensurate increase in the neck-down diameter of the balance of the axle shaft.
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