What could make a strange "winding" noise?

I have a 1990 Toyota corolla automatic transmission. Just yesterday, it began making a weird winding noise somewhere from the engine area. The noise sounds kind of like the noise a fishing reel makes when you catch a fish...that weird cranking/winding noise. It only happens when i shift the car in gear...when i start the car, it runs very smooth, but when i shift it into R or D, it makes that noise. I haven't driven it anywhere, so i cant tell if the noise is constant, but it seems like it is. I cant really tell where its coming from, but it's either somewhere around the serpentine belt or where the engine and transmission join. What could this be and how difficult is it to fix? Thanks