I own a 2017 Thor Quantum RS26 with an E-450 chassis running a V-10 motor. In the thread I posted two years ago about my trip to Wyoming and Colorado,
http://www.thorforums.com/forums/f5/...r-co-9217.html, I mentioned picking up what I thought was pre-ignition while driving at high altitude (about 5800 miles on the clock). It began under load a little after 2000rpm and was gone by 2200rpm. However, when I got home and had the dealership look at it, they determined it was a bad serpentine belt and belt tensioner. When repaired the RV had 7855 miles on it. The problem didn't reoccur until 9557 miles, this time a much louder rattle, like rocks being shaken in a can. This repair lasted only 450 miles when at about 10,000 miles a slight rattle, just like the first time, began to happen. I could get it to rattle by simply putting the RV at 2100rpm under slight load, like a gentle incline.
I just had the RV repaired by my dealer (10,730 miles), but this time they researched the problem and solution. They found that even though there is no factory recall or notice, other dealers were having the same problems on V-10 motors in E-450 chassis. The solution is to install a serpentine belt 1/2" shorter than the original. This puts or tension on the belt and tensioner, reducing or eliminating belt "flapping" and the attendant rattle. The RV now drives as it should, without any annoying rattle at 2100rpm.
Of course, I'll have to watch for the noise coming back in a few hundred miles, but if after a few thousand miles it is still quite, I will consider the problem solved.
Keith Herrington