Just remember that Don's figures are for a single drive unit not a tandem drive and that will naturally give you slightly better mileage as there is 4 less tires rolling resistance and one less differential being powered. But they are a good representation that a chassis speced differently doing the "same" task can get fairly different results.
I personally think they gear these units too fast (numerically low) being as most are in the 3.08 range. I think 3.55 would work better.
I owned a 2000 Peterbilt 379 long hood, big sleeper, true 600hp Cat (not the best reputation for great fuel economy) 18sp, 3.73 gears, 24.5 lo pro tires, 46k rears...fairly heavy specs for a highway truck, pulled a triaxle(102,500lb gross) in Canada and a quad axle(96500lb gross) in the NW states and when driven rationally I could average 8mpg, and as high as 12mpg when running empty.
__________________
2007 Haulmark 3329DS, Freightliner Coronado Chassis, 515hp Detroit, Meritor Freedomline 12speed Autoshift, 10kw Generator, In-motion Satellite.
|