We’ve got a junker of a dishwasher that just started growling fairly loudly during wash cycles. It doesn’t make any abnormal noise when filling with water or drying. The noise seems to be coming from the bottom of the unit. My guess is something motor-related, though I’d love it if it wasn’t.
If you are hearing that "growling" noise check the tube on the back of the dishwasher that feeds water to the middle spray arm. If you see a groove but no o-ring, trying putting a 5/8" ID o-ring on there and see if that gets rid of the noise. I installed that on a dishwasher over the weekend and not only is it quiet again but it also seems to be doing a better job of cleaning the dishes.