Axle spline

[dukeboy440]

Does anyone know for sure the minimum amount/length of spline needed for engagement ina Dana 60 Trac Lock, 35 spline unit, 1.5 inch diameter axle? I'm hearing a general rule of 80%, which would be 1.2 inches if my math is right but I want to confirm.

 

[Locomotion]

I've always heard that spline engagement should be at least the diameter of the axle.....not only for the sake of the axle, but also the spool/differential.