Clunk/Pop on Acceleration and Stop

[ECFR1963]

I have a 2016 Silverado with the 5.3. I have a clunk/pop when accelerating or coming to a stop. I read somewhere about the u bolts not being torqued right but found a range on the internet for anywhere from 70 to 90 ft pds for them to be torqued to. I went with the low end and did 70. It took at least a full turn on each nut to get them to 70. Now it seems to have gotten worse. Do I need to torque them more? Or is there something else I should be checking? 

[rlcole321]

Well you don't live that close to salt water, but the way the bottom ubolt plate is, it can hide a rusty ubolt, check them ( I've seen them almost rust in half), maybe someone can ride in the back to verify if the noise is coming from the rear. Is it 4WD or 2WD?