I have heard these WDMs chugging slowly when slowing down or speeding up. When the train is at full speed then the chugging is also very fast. I have heard these sounds from the toilet of my train, while I was traveling by ASR-HWH Mail. Our 2nd AC Coach was 5th or 6th from the loco and it was a deemer between SRE & MGS. It was 2008 :-D