So I got my replacement stub-shaft. Immediately I noticed that it already had flash-rust on the part.
Also, the hardening section also only appears to be on the transoutput splines area designated by the heat-treatment line. You can also see how the metal is more "blue" vs "yellow" hue between the two.
The replacement Tcase from a 2010 was off an automatic, and I cleaned up the rusty splines with some carb-cleaner. I have a feeling these splines are more hardened vs the stub-shaft. NOTICE there is an o-ring that is suppose to seal this shaft as it seems to prevent moisture from getting in.
Just before installation, I lubed up the stub-shaft with moly fortified grease and shoved it in the Tcase multiple times to completely lube the splines on male to female. I also installed this dust shield onto the shaft as well. ZF 1069-304-046 When actually installing the shaft onto the tail of the trans, I used an impact hammer to start it, then a piece of aluminum over the end with a steel hammer. Once hammered on enough so that
4 FULL THREADS of the bolt can thread on, I then cranked it on relatively easily to fully seat.