A shop installed my new gears, and there was a slight whine. Sound kinda reminded me of a transfercase in low range.
The pinion seal started leaking, so I took in to another shop. The first place had not crushed the crush sleeve properly and tried to use shims to make up for it. That resulted in the pinion nut loosening up.
The sound is gone now.
The problem was actually manufacturing, and then the first shop not knowing any better and not having the right tools. The pinion was slightly too large, so there was no way they were going to get the bearings to seat properly. The second shop had to use the lathe to take a couple thousandths off the pinion, after that everything went in just fine.