rear ratio

[merrick]

Looking at purchasing a new Freightliner Cascadia day cab, Detroit with auto shift, twin screw, noting fancy. It will become a 40-42 foot unit, 18 ft garage, 22-24 foot living. Mostly to visit family across the county. What would be the best rear ratio for cruising about 75 with this unit. I plan on carrying a Toyota Rav or Honda CRV in the garage, still should not be over 50k loaded.

[asitool]

Two articles on the subject I've found helpful:

10-4 Magazine - For Today's Trucker

Working Together | 10-4 Magazine

[bushpilot]

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