Drivetrain whine like it's going out of style

[clean2g]

I believe I figured out what it is - I went to a mechanic that I trust and he showed me that the driveshaft has play in it, like 3/8 of an inch of play when I rotate it by hand near the rear end. So it is in fact a worn pinion gear and I need to rebuild my rear end or buy one.. fun. Thanks for the help

[Pushit2.0]

Rear end: either the pinion or ring gear, transfer case, center diff lower housing/3rd gear in the tranny.

~John