Whining noise 98 Durango?

I have a 98 Durango that I just use as a plow truck. I Dug it out of summer storage and it seems to have a whining sound when it's moving that follows the engine RPM. It's fine in park, and doesn't even seem bad in 1st or 2nd, but once it gets into the high gears it really starts whining out and if I hit the gas hard it'll really humm out. Could this just be air or something from sitting all summer? It still seems to shift fine and work good, just it's quite a loud and never made it when I put it away. Thanks