Hi Chuck There is a crush sleeve (bearing spacer) between the inner & outer pinion bearing that is curshed with a spec. torque to give you spec. inch lb. torque to turn the pinion.What is normaly done when you change the pinion yoke or
oil seal is mark the position of the pinion nut and install (it goes back in the same position )and put a little silicon under the washer nut and locktite.
What might have happen is the nut back off a little or better yet you have a little ware in the side gears and the axel spline and side gears and now that you played with it you are now more aware of it. 1-2 thousands ware on all the mesh gears make a lot of difference.
Ken