[sprink669]

Im new here, just registered! I have a 2001 F-350 PS and love it, but I'm getting frustrated. While going up hills/grades with the engine under load and OD off, I'm hearing what sounds like an air compressor leaking air sound (a hissing sound). I notice this only when I'm on steeper hills. I occassionally pull a 25' travel trailer weighing about 7000 lbs. loaded my rpms are between 2700-3000 rpms. and boost pressure is less than 14 psi. On some really steep passes without my trailer I have heard this sound, I was in OD and going about 70mph with ease when I heard this sound, not sure what to do I turned off the OD and the sound disappeared. I've taken my truck to the shop and explained the problem but nothing could be found. Please help!