quick Help SPLINE NV5600
 

I have a Dodge RAM 3500 2WD, 5.9HO, DRW, 6 speed MT. I have a NV5600 transmission. I am looking at buy a transmisison and two people have one that will fit. I am getting two different sizes of input shaft sizes. I am not sure which one it is and I can't measure the one. The shaft size one person says he has is 1 1/4. He siad that is all that came in dodge trucks. Another person is telling me he has a 1 3/8 measurement and he says that is what dodge had later beacuse the smaller shafts broke easy. My transmission has not been modified or anything like that. Any advise?