Replacing CV axle

Hello, I am working on my buddies 2008 Nissan Altima 2.5S with the 5 speed transmission. I am trying to replace the front driver side cv axle. We are to the point where we need to get the axle to back out of the hub. However, it seems to be rusted on inside of the hub. It should just slip right out of the hub and then we can remove the inner side from the differential. We have hit the end of the axle with a sledge, heated it, sprayed with penetrating spray and tried an axle puller. We have had no luck. Yes the axle nut is off and we can swing the knuckle from side to side to allow room for the axle to slide out however it is seriously stuck. Is there anything we are missing like a snap ring etc? We are stuck and there are no tutorials online. Any help would be appreciated. Thank you