Hi All I've seen some threads on here about rear diff noise but just wondered if anyone can tell me how likely the noise mine is making is the ring gear or the Torsen anti slip. I realize its hard to tell with this thread but just wondered if anyone has had this problem?I have an 18 3500 with the Cummins/Asin and a 11.8 ring gear. Mine has very light whine comes on around 30 after its warmed up a little and after its fully warmed it make a very light whine around 50. I will admit that I didn't get the first fluid changed until 40 k. I was surprised that the fluid was as black as it was. Then changed it again at 50k dirty again. Also did an oil sampling at 50 k and it came back without a problem seen. Has anybody had this issue? Would switching over to a thicker weight oil benefit the situation.?Has anyone tried a heavier oil.? My truck just turned 60k so still a young pup but out of warranty . We tow an 11k lb trailer about 5 times a year and do plow our shop and driveway. when it snows. I am Running Amsoil synthetic 75-90 right now. Thanks for your time.