Every time I've run a timetable service with the SD40 on Clinchfield, I lose engine audio. At the start of the service, everything appears normal. I prepare the train and wait for the brakes to release. Then just at the point of wheels beginning to turn after applying power, engine audio cuts out either entirely, or partially (as though I can sometimes still hear the other power units behind). If I wish to continue the service, I have to do it with what little audio remains, which has no correlation with throttle level, so as you can imagine, that's a pretty dismal experience. I have run the SD40 in one of the scenarios, and audio was normal.