We bought a 1987 Coachman 28 ft class C last fall.? We have only put about 1500 miles on it after alot of project adventures with it this spring.? Now it appears the exhaust pipes (front and rear of the muffler) are forcing themselves INTO the muffler causing leaks in the muffler.? This big old Ford 460 really roars now!? The muffler is pretty new so it isn't showing any signs of rust...what could be causing so much flex in the under carriage as to drive the pipes inside the muffler?? Has anyone else seen this before?