Some of the things that can make them hard to shift can be rusty or galled shift rails in the shift cover or the wronglubricant. When this transmission was produced it was designed for straight mineral oil. Using the wrong lubricant can make them hard to shift. I now use 50 wt synthetic on all of my Fuller transmissions. They last forever and shift much easier. Just because the truck is extremely low mileage doesn't mean you can't have bad bearings in the transmission. The smaller fuller 10 speeds were also more difficult to shift because of the higher rpm's of the engine. Todays over the road engines operate between 1200 and 1600 which makes them easier to shift every generation of fullers shifts easier. I learned to drive on fullers in the mid 60's without using the clutch. The old engines were so underpowered and had such a small operating range that a person was constantly shifting and shifting without a clutch was the way the old timers of that day did it. Old habits are hard to break. I still drive one of our trucks occasionally and I only use the clutch to start
