Folks,

My 64 d100 stepside short bed has a driveshaft that is 4 inches in diameter, tapering at end to about 1.5 inches, where a yoke attaches to a 15 splined connection. I read about 18 splines, 23, 29, etc, and wonder if you wizards know if the 15 spline is limited to trucks?

thanks
rock

The 18 and 23 splines are the number of splines on the input shaft for the transmission. All the manual transmisson have the 23 splines execpt for the A833 4 speed behind the 440 and Hemi which had 18. I am no sure what the number of splines are on the ouput shafts, but the A833 4 speed and the A727 share the same number and diameter and the 3 speeds and A904 share the same number and diameter and there is more then 15. It sounds to me, that you have the U-Joint that bolts onto the output shaft of the transmission. In that case that sounds about right for the slip yoke that is used in that setup. And yes it is a "truck" only setup.