Clink Clunk when putting in gear

[bigmac73]

sometimes i get a clink when I put my truck in gear either FWD or Rev, I thought it was the U joints, but I got under neath they all feel tight, I tried to shake and move them up and down by hand, no kind of movement, at all.

any thoughts, maybe my pinion gear is wore, I had the gear fluid changed a couple of years ago, and the garage said everything looked good inside no issues or shrapnel was found

U joints and carrier bearing are about 3 years old