Bad Grinding Noise from Front End

[AKpath]

Hey all, new Pathfinder owner here. 1998 XE 4x4. Here's my situation. Trying to figure out the source of my horrific grinding noise coming from what I've gathered is either A) CV axle

B ) wheel bearing or C) front diff. 

 

Truck is in really good shape, low miles engine recently swapped, drives great yadda yadda. Driver side CV axle was in the trunk when I viewed it. Boot was torn, owner said he took it out a few days earlier because it was making a bad noise because it lost all its grease. Makes sense. He showed me a video of the 4x4 working so I took his word for it and bought the truck. I drove it home over 100 miles (didn't realize the insane danger of this move until about halfway through the trip, scariest drive of my life). Anyways I made it home in one piece, the truck drove amazingly up and over the i80 pass from the bay to reno, no weird noises, no grinding, no vibrations from the front end. 

 

The next day I got a CV axle from the junkyard from a 1999 pathy that looked and felt great, clearly plenty of lubrication. Installed it, went to drive and there was a gnarly grinding noise that is directly related to speed. Starts immediately when I take off from a stop. 

 

Diff fluid was VERY low, topped off. Still grinding. Thought maybe I bent the dust guard for the brake rotor, it was bent but bending it back didn't change anything. Did notice the passenger side CV boot is torn and bone dry inside. That seems like an obvious culprit but my question is why didn't it make ANY noise the entire drive home? Wondering if anyone has any thoughts, although I will probably just replace both cv's with new parts once I get my money up. 

 

It also seems like the passenger side axle seal is leaking at the junction point to where the CV axle mounts. Is that a hard job? 

 

Thanks all, excited to get to know these trucks better! 

[AKpath]

Update : it's much worse going forward than in reverse...