I often think back many years to when as a kid of 19 yrs I thought I had hit the big time, driving a semi.
The tractor was a '56 Ford F800 "Big Job" with a 272 cid (4.5L) V8, 5 speed transmission, 2 speed axle and air brakes. The factory tachometer was marked with an operating range of 2400 to 3600 rpm, it had to be turning at least 3000 rpm to develop any power. At legal top speed of 50 mph it turned about 2800, but the slightest grade required an immediate downshift and higher rpm. And that was almost 60 years ago, engines have improved drastically since then.
2400 rpm isn't much for your engine, it would actually be happier running faster under load.