Interesting on 4340 vs 1541.
@mrblaine, I think a few of us are wondering why 4140 is preferable over 4340 for the Dana 44. In trying to read and comprehend materials engineers on this topic, I came across this quote.
"4340 is typically considered to be tougher than 4140 in the quenched and tempered condition. This result is more from the fact that 4340 has higher hardenability and is more consistent in the heat treat response, particularly in thicker sections, than the differences in chemical compositions. 4340 is also typically produced to higher cleanliness standards than 4140, which is another big contributor to the toughness.
In my experience, however, in sections where heat treatment results in >95% martensite, with comparable levels of cleanliness, and tempered to equal hardness and strength levels, 4140 will have a higher impact strength than 4340. This is contrary to “common wisdom”, but I have test data that supports it. This is mostly a trivial point, however, since in most applications where 4340 is preferred over 4140, the section thickness is such that the 4140 might not fully harden, but the 4340 will."
Is this your understanding? Are our axle shafts treated by quenching and tempering? Is the section thickness of an axle so great that 4140 might not fully harden? Or is it thin enough that it does fully harden and that is why you are making the recommendation of 4140? Greater impact strength. Nothing is mentioned in what I read about ductility, but I am supposing that is maintained in the heat treatment process.