This differential is not a locked differential meaning both tires are not going to spin equally. Only the one with less traction will spin. So, when there is no friction on them because they are in the air, only the tire that has less drag on it will spin so that is not an issue.
However, this does sound like an axle issue. So, if there is a noise and vibration plus there is movement from the axle, I would investigate this further.
Can you get a video of what type of movement you are seeing with this? Those axles are slip yokes so the axle slides in and out but should not have much movement to them.
I attached the info below on how to replace them because this sounds like where it is going.
Let me know and we can go from there. Thanks
Images (Click to enlarge)
Wednesday, October 13th, 2021 AT 2:26 PM