ALLFK,
I also have a 2011 Grand Canyon and have the same sound. Yesterday, I had Jerry from Lippert at my home to replace my axles and we both tried to find the source of the sound. Jerry found what we think is the source of the sound. Believe it or not, it was the foot pad at the bottom of the front leg. When we shook the RV, the popping sound was heard behind the propane tank. I guess as the outside temperature changed, the foot pad caused the popping sound. Jerry jacked up the RV from under the frame and used WD-40 on the foot pad at the bottom of the leg, moved the foot pad around while it was off the ground, then removed the jack from under the frame, we shook the RV, sound gone. Time will tell if that was the source of sound, but the popping sound stopped. My ToDo list will now include spraying the foot pads every once and a while.
Great job Jerry on doing the axles and tracing down the sound.
DougS