New "moaning sound" from our Jake brake

While on our winter adventure I exited from a high RV park pad without going all the way to proper ride height and drug the bottom of the muffler and one of the skid extensions on the bottom of the frame on an RV concrete pad. Now the Jake brake makes a different sound when engaged. The best I can do is to describe it as a moaning sound, louder at very low speeds than at higher speeds. Any idea what this might be or what I might need to do to correct it? No damage under neath that I can see, just some scrape marks on the bottom of the muffler and those skids on the bottom of the frame.