1998 Dodge Durango V8 Four Wheel Drive Automatic 19800 miles
Sometimes my 5.2 litre after you start the truck, let it warm up a bit, then put it in gear to drive, it sounds like there is an airplane turbo-fan under the hood. A really loud " blower" noise, like what it sounds like standing beside the vent of a large industrial fan/circulation duct. It gets louder as you increase the gas and will keep at it for sometimes as long as 30-45 minutes. No gauge fluctuations, no warning lights, no noticeable performance slough. Probably not a BIG issue, but I have found the little ones - if not dealt with - GROW UP to be HUGE!
These are normally quite noisy when the thermostatic fan kicks in. Believe it or not, you can hold the fan with your hands as someone else starts the engine, assuming the clutch is not seized. I've watched people do this but I'm too chicken to try it myself.
As the engine warms up, you will feel the increasing tug of the fan trying to turn. Some vehicles make more noise when the fan starts to move more air, some make less noise as the clutch slippage decreases.