underhood noise when going up hills

[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!

[strokermann]

it might be when you truck is in a lower gear and making boost and when you hit od the truck goes down in rpm you hear teh turbo realeasing teh air. mine does it all teh time. or when you stomp on teh pedeal and release it right away you will hear teh turbo dump the air.do you feel any power loss. are you on a steep grade in overdrive. maybe your just make boost and that is what you hear is teh turbo spooling up.

[2005F250]

It's your wastegate or one of your turbo boots might have a hole in it.