clunking noise from rearend

looking for help on a few issues . 2012 , 2500 regular cab. 940 miles , having issue with when going into gear from park to reverse , neutral or drive i get a clunk from the rearend , also when taking off from a stop and give it the gas and then let off quick trans shifts back to first and get a clunk again. is this a trans issue or rearend.. also when driving truck at highway speeds , when hitting about 80 mph , the truck gets a growling noise from the rear end.. no vibration issue , just noise. looking for info , going in next week for a new abs module to be installed... just dont want to be b.s. to death about these issue's from dealer.. any help would be appreciated.