The undercarriage of your unit should be included on your RV checklist and inspected at least once a year and possibly more depending on how you use your RV. To start inspecting the undercarriage of your RV, you should create an RV checklist that includes every aspect of the underside of your unit, what needs to be inspected and what to look for.
Your underside RV checklist should start with the exhaust system. Look at pipes and connectors ensure everything looks good. Cross off from your RV checklist that you have verified that all hangers are present, in their proper place and not damaged. Visually verify that all wiring harnesses are connected and grommets are in place. Look closely at hangers and braces for the exhaust pipes to ensure they are fully supporting the exhaust system of the unit.
As you work your way along the backside of the unit and further down your RV checklist make sure all brackets and leaf springs are in place. It is not uncommon to see where these brackets break and to have one of the leaves coming out. Visually inspect the airbags, shocks and brackets ensuring everything looks good and is in the proper place.
Next on your RV checklist is to go under the back side of the unit look at fuel fill, clamp connectors and rubber tubing and verify that there are no leaks. Check the exhaust system of the generator making sure there is no rust or any holes in the tubing that could allow exhaust fumes and dangerous carbon monoxide to enter into the RV from under the coach.
Look at the egress/departure angle for damage. Look at the mud flaps and make sure they are present and damage free. Finally visually inspect the hitch.
When conducting an inspection of the underside of your RV, make sure to let the unit cool off after driving. You do not want to be under the unit while it is still hot from operating. You should be able to conduct a thorough visual inspection of the underside of your RV by using a simple creeper.