I've seen transmissions stuck in high before. What usually happens is the input shaft dog teeth will wear notches in the front of the 3-4 sleeve from the constant on/off the throttle, after a time the dog teeth on the input shaft will lock into the notches and will prevent the sleeve from disengaging the dog teeth.
Bingo, this is exactly what has happened. 3-4 synchronizer is the brass that is in the transmission. Just got thru looking at it and it's the problem. I'll be calling Brewers in a couple days.
