Whhhoooaa there!
Before you yank the shafts out check your rear prop shaft UJs, these are the usual suspects to clanks and clonks. You'll need to chock your wheels and take your hand brake off to test it. Get under the truck and give each UJ a good waggle. If there is play in the UJ you'll know it.
It could also be the A-frame ball joint as well.
UJs first though!
