8.75 Diff Questions 2nd try

First thing to do is like Guitar says, swing her back and forth and if the sound doesn't change then it's not the axle bearings. This is also how you check which hub bearing (left or right) is bad on a front wheel drive car. Then pull the pig and get her up on a bench, you'll need a mag base dial indicator to check for backlash and also to check the pinion for up and down or in and out. When she's on the bench you can tell just by looking whether it's a cone or clutch sure grip. I suspect it's one of the pinion bearings.