Call Kwikkie and get some new bumpers. They are easy to change with a 7/16" wrench. The hard part is getting the steps to stop half way. Have a friend shut the door while you turn off the chassis batteries. Might take a couple of trys to get the timing right but it can be done. Then it is a simple task to crawl under, remove the old bumpers and install the new ones. Should take 15 minutes max.
There is no amount of lube that will get them to stop squeaking for any length of time as when the bumper wears out, you have metal on metal.
Been there done that.
2002 Country Coach Intrigue