I am the proud frst time owner of a 2005 Sliverado Duramax/Allison CC. I tow a 9000lb Jayco fifth wheel with no problem. However the other day I was towing and heard this sound like a jet taking off. I actually thought it was a little rice rocket passing when I realized it was the truck. Someone told me it was the fan clutch engaging and sounds like a jet taking off. I was in tow/haul mode the temp outside was approx 80 and humid and the tranny temp was approx 190-200. Does this sound right?

the fan maybe????

I will move this to the appropriate section. Congrats on the new truck and Welcome. Yes you are correct about the clutch engaging. It will do that from time to time...

Yeah it can be irritating but it's normal..

Be happy your fan is kicking in. There are some here that the fans is not kicking in and without the fan it WILL overheat!!!!

My fan clutch was engaged most of the week, It has been pretty damn hot where we were working, it's normal, don't sweat it...