New gearbox noise after diff locker install?

[Deadduck]

It is 4wd that photo was off internet was too wet to lay under car the shiny bit moves in and out and I had done the seals when I done clutch but there is up,down,left,and right movement there u said there should be none? I felt another one same place and that had same movement? All ujoints are good no play. Noise happens in 4wd and 2wd. Just the whining noise that can be heard under acceleration