Sorry, I wasn't subscribed to this post and forgot about it. PM me tomorrow between 8-5 or call 405-424-RACE, and I'll ask you a few questions and maybe narrow down your problem.
Hey sorry to hear about your problem. My bro has an 01 7.3 with the 4 speed auto in it. His started doing the same thing and he rebuilt the tranny with upgraded clutch packs and made it ready for some more plowing.
going from reverse to drive alot during plowing has a bad effect on those trannys. His was sitting at 80K when this happened.