My 06 hd 6.0 has some type of issue with the transfer case I guess.. That's where the sound is coming from when I swith to r from d or vise versa it has a bad clunk. And I grabbed the driveshaft and it has slack in it but the u-joints looked tight? And also when I let off the gas about 3 outta 6 times it makes a loud grinding noise & at low speeds there is a clunk clunk clunk (not that loud)