our (Freightliner Columbia MBE 450/1650 hp/tq) is equipped w/ the 12 speed Meritor ZF Freedom Line SmartShift and a 3.21 rear...and at 70 MPH we turn just under 1500 RPM.
at 65mph we're turning 1300 RPM
Although I havent recorded the RPMs at 55mph I know its a sweet spot for MPG (13.3-ish from Atlanta to Destin) - at 70mph we consistently achieve 9.9 mpg (hand calculated and reportedly better than most).
I'd love to be able to run 75 at 1300
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Don R.
'04 Haulmark (M42386) 42', 2 slide, 10kw - Pictures
'04 F350 CrewCab Longbed 4x4, 50g aux tank & gear vendors dbl over
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