Get your tickets to THE BIG THING 2026!
Both axles that could be back there (D35 and D44a) are both crush sleeve axles.
This means that the pinion bearing preload is set by 'crushing a sleeve' when tightening down the pinion nut on install.
To properly do this, anytime you remove that nut you're supposed to put a new sleeve in as well, then tighten it and get the bearing preload right.
Which means you get to rebuild an axle! Perfect time to sweet talk your wife into letting you get a locker!
Crap....thats what I was worried about.