rear u-joint

just to be clear - no play in joints at all - I could move yoke a bit in/out of differential. ok, also, I removed inspection cover on clutch - I could wiggle the TO bearing a bit - how much should this move? Did not note any grease/oil on anything I could see into. Saw a few tiny shiny/metallic specs inside the housing - clutch material or maybe from the bearing?

The yoke should not move in and out of the differential, which differential do you have ?