gear slapping?

i finally put the finishing touches on the twin sticks today, but have noticed a new issue in the transfer case. it seems to whine a bit louder than before, up to a point and the gets real quiet. it also seems to slap gear faces when i go from gas to coast. there seems to be a bit of play betwen those two faces somehow.

can this be caused by a faulty endplay measurement? i checked everything and according to the dial it was good. but the slapping and new whine have me thinking i was getting a bad reading and am a bit to loose. i've looked around for a bit trying to find a problem shooting guide but can't seem to find the right words on google... any know a link?