mods to 727 are as follows:
In 1976 to increase strength the angle of spline teeth was changed on the output shaft it went from 45 degree internal splines on a 37.5-degree shaft there's preciious little contact area. The sharp splines act as a very efficient cutting tool, resultling in the destruction. It gets worse in 1994, the spline tooth angle changed yet again, this time to 30 degrees. This occurred also in the 727's overdrive spinoff, the A-518, as it was beefed up to accommodate the beefy new 360 magnum and V-10 torque monster cummins diesel mills. And yes you can screw up a 518 the same way.
The fix once you know it is simple use the four pinion planetary with same spline tooth angle as your shaft or swap the shaft. Just remember to use the same thrust washer setup designed for that family. For more information go to www.aandatrans.com. All this information is in the feb 2002 issue of mopar action if you can get a copy do so and read it. Story by Richard Ehrenburg page 54.
