Also the basis of this post looking for help: https://www.wranglerforum.com/threads/front-axle-shaft-wont-slide-in-2010-jk-rubicon.2455499/
So got back to installing the new axles today. Passenger side slid right in, haven't buttoned it up until I know the drivers side is in and that I don't for some reason need to disassemble the diff.
So first up on the passenger side...ran into an issue that beyond the end cap rag that did a good job keeping dust out when had put in a paper towel and plastic bag (bubble wrap?) to keep the oil inside the diff :D
Finally after about an hour I realized just what I needed was a plumbing rooter router thing...and also remembered I own one :D
Grrrr...not going in.
Had this happen when I replaced u-joints and since it was going to Sorel's anyway had them fix it.
But I replaced the diff seals and had no issue sliding the shafts back in :/
So I scoped it, looks like a seal to me.
So then it was time to measure (you know high tech before low tech :D )...
The 12" measure is along the tube side and my interpretation is that is the seal.
The 17" is in the center, and that is about where the oil slinger at the end of the axle shaft should be.
Overall I think I'm about 1" maybe 1.5" shy of where I need to be, but there is 2" of splines so they must be getting partially engaged? This is basic math right?
Bonus! Look at the diff to see if I could see anything and saw some Helicoil looking things backing out so I'll have to research that.