Sounds like the forward clutch pack could have burnt up or just plain gave out. Could also be the forward sprag. At any rate, I would think a rebuild or reman is in order.
Could it be caused by the engine overheating? Well, yeah. But proveing that would take an act of congress and a few saints! Then you would have to convience the dealer that they are responsible. It would be a daunting task, but if you had the proof - then I guess it could be done.
