i dont think that dt466 with a six speed has a set rpm split between gears, what i mean is the lower gears may shift with a differant rpm range than the higher gears. i drove a ih dumptruck once and had a real hard time with it at first, untill i found that not all the gears fit with the same rpm split. i agree with the other post that you should try floating each gear untill you figure the rpm splits ......happy trails
I would say that completely ignoring the gauges would be a mistake, especially for a new driver. I found that by using the gauges as a guide, but first listening to the engine, floating gears has gotten much smoother for me. Between listening to the engine and watching the tach, I don't have to check the speedo as much as I used to. Also, I never (not that I can recall) have to wind my engine to 1800 to shift. I know that different trucks have different needs, but that seems awful high to me.