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Dynaflow Yoke Spline Size?

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Does anyone know the diameter and spline count of a 1956 Dynaflow yoke? Put differently, what is the diameter and spline count of the front of the driveshaft?

 

Also, did this diameter and spline count change throughout the years of Dynaflow production?

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I do not know the specific answer to these two questions. But if you are looking for a driveshaft that easily interchanges, i dont think there are any. 

 

'56's used a fine spline for the first time. Prior years had a coarse spline. 

 

"57"s  and up used a two piece shaft with a universal in between. 

 

I might suggest either unit could be made to work but, would probably require changing the entire rear axle/ torque tube assembly. 

 

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I think the OD changed mid-‘56. Our EARLY production Special has a smaller diameter than the standard seal we got with our torque ball kit. We had to source a seal locally (wasn’t hard to find). 

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I dug out the Dynaflow from the parts shed, pulled the torsion ball, and miced the yoke ID.

 

For posterity: 1.2185" diameter x 28 spline. The propeller shaft diameter will obviously be slightly smaller for clearance, but I don't have  a propeller shaft to mic (hence my original question).

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There is an issue stated in Buick Service bulletins. The fine splines would strip out if to much force was encountered. Check splines on shaft and internal on u-joint as they can also be twisted a bit like some licorice available in candy form. I think 57 also had some same issues? Anywho, somethin 2 B checkn when ur lookn 2 buy stuff. The 56 dynas are all the same length thru the different models. 55 Sep/Cent are approx 1" shorter when measured same place. 55 Super&Rdee are the same length as 56 Dynas. If you can find a Motors 56 flat rate manual, they list Dyna parts with interchange nicely grouped so you dont have to b a research librarian to find that info. Very much simpler to use than the Hollander manuals to find same info. Good luck!

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