The AC motors I ran--SD70MAC, ACE and several GE versions, could not be "plugged". When under power with the reverser forward, if the engine or train began rolling backwards, it would instantly drop its load. This happened to me once while my train was stopped over a hogback and I needed to change directions. I came out on power with both head end and the DP, but not enough on the lead. When the slack ran out on the head end, that power dropped its load and rolled downhill forward, while the DP was pulling most of the remainder of the train backward. BAM!! The drawbar on the 4th car just exploded. The worst about this incident was that it had to happen in front of the BN depot in Amarillo. After we set the lungless car out, it sat on the depot track for a week before being taken to the RIP track. It became "my" car.