Hello I hope by asking here someone can help me out. I have a 2004 Jeep Grand Cherokee overland. Whenever I turn you hear this grinding noise towards the back. What is it?

and you took it back to aamco and they said what????

when the problem first started i took it to aamco. they gave me another transfter case (247) and we got to drive it for a few days until it started again. took it back and they gave us another. drove it for a day or so and again the problem came back. did that another time and they told us that they rear axle was destroyed so they gave us another transfer case and replaced the rear axle. all these parts were used by the way. then we drove it and again problem came back and not even they wanted to deal with us. did some reading and decided to do the job myself. went to a junkyard found a 242 transfer case. swapped out all the pieces i needed from the 247 to the 242. it continues to do the grinding noise. i've replaced the front axle shafts and the front wheel hubs. i removed the rear axle pumpkin cover and none of the gears look grinded or scratched up. i've put the mopar oil with the limited slip additive. i don't know why it continues to do the grinding when turning. it only really does it at the end of a u turn more than turning normally left or right.