as of now I'm assuming the noise is my differential or I need a tranny rebuild.
I'm with HGB on this one... I bet the small taper bearing on the bottom of the output shaft is shot.
Pull it apart to fix it... driving it can lead to total failure of the bearing, and if a roller gets loose and gets between the R&P it'll kill all sorts of expensive parts in there, so stop driving it now.
The helical design of the teeth cause thrust forces axially along the shafts... the gears want to slide up and down away from each other, basically.
The R&P gears are helical... the thrust forces will shove the output shaft towards 5th gear under acceleration, increasing the load on the large taper bearing that secures the shaft. These forces reverse any time the engine is being driven by the trans. When in gear and off the throttle, the momentum of the car will cause the engine to rev, just like downshifting and letting the clutch out revs the engine up. This is when the thrust forces reverse in the trans so when not accelerating, the output shaft is shoved away from the large bearing and into the small bearing.
As soon as you let off the throttle in your vids, the thrust forces reverse and load the small bearing on the output shaft. As soon as you apply throttle to make the engine drive the trans and not the other way around, the forces go back to normal and that small bearing is unloaded and the forces shove the shaft into the big bearing, which is better sized to cope with the load.
That small bearing is almost always worn in the trans I open here. That bearing is why I started having all the bearings I keep in stock cryo treated. I had read that some taper bearings have experienced 300% increase in service life due to the increased wear resistance that cryo offers, so I started having the bearings treated, just as an attempt to negate the accelerated wear of that small tapered bearing.
