I have the same truck and same problem. It happened slowly over time and got worse as time went on…. Took it to dealer with 6000mi still on warranty. They thought it was tear end, replaced it… nope… they kept it 7 WEEKS!! and could never find the problem. Tried Picos thing and everything…. Said they couldn’t do anymore… I picked it up and was told it was not any part on truck. I took it to an independent transmission shop and had tranny services….. noise GONE!! Gone for 8000miles and it just now started again…. Now what?!!!!