LOUD r50 rear differential whine/whirring

[Calr]

I wanted to do the 4.3 to 4.6 swap, picked up a pathy 4.6, superpacked it, put it in ( along with the front differential, it whined and whirred extremely loud. Took it back out, set backlash even lower to .005 and it still whined, usually only on acceleration. Took it out and out the original back in to drive around town( disconnected front driveshaft). That one whined as well, instead it whined on acceleration and coasting 15mph+ (basically same as the other.
Now that had me a little confused, why would my original differential whine too, it never did before! ( i also had a hard time hearing it because my front wheel bearing went out, but at lower speeds I could tell it was there. Went back to the junkyard, got lucky and got a 4.6 lsd, never touched the insides. It whined and whirred at all speeds, pretty loud too. posted this on the Facebook group and asked my cousin who is a mechanic. He had to ask his nissan friend cause he was a little stumped.

- only touched the insides on the first differential, other two were just taken in and out

-used 80w 90 with slip additive

-kinda of hard to spin the wheel currently with the 4.6 lsd in

-can hear a very light scraping noise coming from differential with the wheels up and driveshaft taken out.

-current oil every time

[Calr]

Could I be doing something wrong somewhere along the line? One thing I thought was strange was when I push the axles back in, it makes this air releasing noise, like air is being pushed out.

[Calr]

Update: sounds like it may be from pinion bearing. Put original diff back in and there is no whine or whirring. In fact, its not too bad, but its still there, and it only happens on acceleration.