Look at your compressor drive plate. The visible front plate on your ac compressor pulley. Mine has a spring-steele "three-hoop" pattern. One of the "hoops" are broken. When you turn the ac off, this is supposed to ever-so-slightly pull the drive plate away from the compressor clutch when the ac switch is turned off. Since one of mine is broken, then it doesn't pull away from the clutch evenly and is slightly cocked sideways and drags on the compressor clutch sometimes as the pulley / clutch freewheels (compressor off).

I have a new drive plate I ordered from Isuzu, but I haven't located the puller tool I need to replace it yet. It only has 1 bolt in the center that holds it on, but it has to be pulled off / pressed (or drawn) on... Most days now, it doesn't drag / growl, so I'm leaving it alone for now. Hope this helps.