First, there doesn't appear to be anything wrong with my tranny - 2002 S80 T6.

When I put my foot on the brake to put the tranny into gear, I can feel the linkage "unlock" the gear shift lever. There's also a click when this happens. I also feel it occasionally when I slow down and brake to come to a complete stop.

Is this normal or is there something loose in there?

 

That is normal it is call the Shift lock setup. When you are slowing down and feel it that is the Reverse lock out function disengaging.

But it is all normal.