What is the optimum RPM range on a 6.2? I am thinking of swapping over my 3/4 running gear into my jimmy. I would be running 4:88's w/ a 700R4 and 35" tires. That would put me at around 2100 rpm @ 65 mph. What rpm do these diesels normally run at freeway speed? I'm not sure of my gear ratio now, cause I haven't jacked up the rear end and counted revolution, but w/ 31' tires get up past 85 easily. I know I have heally high gears.

at 2100 i would think with your tires and gears that would be about perfect.

You want to be between 1800 and 2100 rpm for optimum fuel economy and engine life. 2100 at 65 is good if 65 is all you are going to do, but keep in mind that you may want to drive faster than 65 mph (most people do these days, although I don't know why).

My truck runs something like 1800 rpm at 70 mph with the setup in my sig.