I'd say 2800-3000 is about as high as you'd want for extended periods, less would be better - with the 3/4T gearing, 50-55 is what I'd expect and what the truck was built for

Bill


Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics