Hi BobnBet,
If you search the forum, you'll find many threads on this subject. The problem is with the Lippert auto-leveling system landing gear. It's thought that there are micro-movements (probably temperature related). When on concrete, the pad can't move easily, popping when it does move.
At the North American Rally in Gillette last June, the Lippert Rep told us they are investigating this and trying to find a solution. People who have been following up with Lippert report that so far, they haven't got it figured out.
Here are some suggestions:
Call Lippert directly to get a case opened. The thought is that if you run out of warranty before they have a fix, the open case should cover your warranty claim when they do have a fix.
Some of us have noticed that the popping is worse when the landing gear is extended further. Putting down a stack of 2x12 boards, or other type of leveling blocks shortens the extension and may help.
Some have had success (some not so much) puting down inexpensive plastic cutting boards from Walmart ($1-2 price range). The cutting board seems to allow micro-movement of the jacks alleviating the noise.