Rear-End Gear Ratios

[ZeroNthedark]

(08-06-2017 )Hammerhead Wrote:  Hell, I get 7 USmpg with my big-rad non-aero truck with my wind grabbing parachute of an equipment trailer empty w/ a jeep & booster stacked up weighing 70k. That's at 55-60 with 4.10 rears w/11R22.5 not low rolling resistance drive tires pushing those great big definitely not lrr 385 wide steering tires.
If you pull a box trailer, especially if you've got the side skirting and stuff you should be kicking my @$$ all over the place in the fuel mileage game.
The "old myth" that countless truckers spew about "I get better mileage at 70 than I do at 60" is such BS I don't even laugh at it any more. Physics doesn't change, that's why they call them "Laws of Physics". A physics fact, as speed increases linearly, aerodynamic drag increases equally, however as aerodynamic drag increases linearly, the power required to overcome the aerodynamic drag SQUARES!!!

This is a question I've been wanting to ask for a long time, but not known how to bring it up...

My daily driver is a 2005 Pete 379 tri-axle dump truck(so a brick, basically). It has 425 steers and 11R-24.5 drives with 4:10 gears pushed by a 475 CM 870 and a manual 18-spd. Now I realize Hammerhead has had work done to his, and mine is in serious need of help, so we'll discount that for a minute, but why does it seem that if I drive 70-ish, at around 1600 RPM all day, my mileage appears better than if I go around 55-62, which is either 1400 in top gear or 1550 down a half gear? I usually try to keep my Boost under 30, mostly around 20, and Pyro hovers around 800 on tall hills, sometimes 850. This is in Western PA, so it's pretty much you're going up a hill or coming down. Very little flat ground on my runs except for I-76 between the 13 and 75. Which I don't get very often.

Sorry if I got long-winded or hijacked the thread, just looked like a good time to ask.

BTW- Best mileage I've managed is low 6's. Usually around 5.5.