Like the title says, cant seem to get the splines to seat or at least go deep enough. I can still see the grooved ring above the splines and can’t seem to get it any deeper in. I pulled it out and as near as I can tell it’s identical in length, spline count, etc. Not my my first axle job, but I’m stumped and could use some ideas.

 

There are 2 different inner cv shafts, outer cv joints are the same though. Not sure what the counts on them are but if it's not going in I would assume it's the wrong one

 

That was my first thought as well, but my understanding is that there’s a difference in length in the other version. Having checked, length is the same so my thought is it’s the right part. Of course it could be after market incompetence, but open to other thoughts as well.

 

When I changed from the midland to the getrag I did not notice any difference in length, only that the inner cv was the only difference. Have you tried gently moving the opposite wheel while pushing the cv in? They can take a sudden shunt in to get them in, almost trying to catch it by surprise lol.

 

I had a similar issue with a remanned axle. There was debris under the c-clip which prevented it from squeezing down.
Remove clip,clean groove. Replace the clip with a new one - you can't remove it without damaging it - and also they're one time use only.

 

When we replaced the faulty aftermarket passenger side CV axle with a GKN, I too struggled for a bit. Keep the axle on the same plane and as straight in as you can. If the axle is going in at even a slightly off line, it will bind.

 

+1 on moving the opposite side or try to slowly/gently rotate the axle by hand if you can and the little by little try. hope you get this sorted.