Stephen, Someone advised me that Klune-V has experienced two broken transmission output shafts with their boxes, and they were both 23 spline Dodge. Klune confirmed they had experienced 2 broken 23 spline Dodge shafts. I spoke with Hughes Performance and they advised me that in a 4x4 application a hardened 23 spline output on a 727 TF should handle my approx 400 h.p., large tires, and a Doubler system with no problem. They advised the mentioned breakage was probably because the shafts were factory. Will a 23 spline 727 TF output stand up to 44’s, 400 h.p., and a Doubler? I would think a U-Joint would blow before the transmission output shaft. I already have a 727 with a married 203 (1979 Dodge) so I think the Doubler is definitely the way to go, but am concerned about the shaft strength where it feeds into the 203.