The left rear of our 1984 dropped down such that the tires were rubbing on the underside of the body. After stopping I was able to raise that corner with the leveling system. Could a defective leveling system valve cause this problem? A friend that converted a bus said the buss had blocks that stopped the body from comming all the way down when the air bags were not able to hold the body up and provide safe clearance. Can such blocks be installed on a Newell?