Well I have had this popping noise when I placed my truck in gear.....either in DRIVE or in REVERSE
Good thing I crawled under my truck today and checked the torque on all the control arm bolts, both at the axle end and at the frame end
On the upper control arm, on the passenger side, the frame end bolt/nut was VERY loose.....like barely threaded on, NOT GOOD!
Torqued everything back down and the noise is gone
Guys PLEASE double and triple check the control arm bolts if you have popping noises......not to mention for the safety concerns!