Truck / Trailer question?
The trans wasn't rated for the torque of the H.O. motor. That simple. There were a lot of owners doing upgrades to the engine for more power, so it's not rocket science why there were failures. :(
I haven't heard about a deal with Volvo. I would suspect an Allison before Volvo but you have to remember that DC owns; Freightliner,Sterling,Detroit Diesel,Mercedes. So if there were a heavier auto on the way it may come in the form of something they currently use in one of the large overland trucks.