normally quiet it suddenly developed a very loud roar. Manual says to give it some time for it to chop up the difficult food. I got into it and found some sort of plastic debris that it couldn't chop. Cleaned everything out but still the noise. I removed the chopper screen and impellor just to see whether that was the noise - it wasn't. It looks like the motor/pump assembly is relatively cheap, has anyone had the experience of replacing this on the Kitchenaide?

I replaced the motor assembly and it is now as quiet as the day we purchased it. I went ahead and replaced the inexpensive chopper assembly while I was in there. I pulled the unit from under the counter because I wasn't familiar enough with the clips to know how to pull them out without seeing them. 30 minute job to swap it, not including the pulling and putting back under the cabinet.
Thanks for the help.