I have a 2006 Thor Four Winds 6.6L diesel based on the Chevy C5500 Kodiak chassis. After 14,000 miles I have minor squeaks in the dash and somewhere around the drivers seat. There shouldn't be any major squeaks or noises. We love ours, but it IS a truck.
We test drove a Jayco Seneca on the same chassis and the power brake booster noise was continuous. That was not right. Only time I hear it on the Four Winds is when I push all the way down hard on the brake. This seems normal.
2006 Fun Mover RV on a C5500 Kodiak chassis with a 6.6L Duramax LLY and Allison 1000 tranny, remote door locks, Steer Safe and Henderson Rear Trac Bar