Engine Cruise RPM

[Lonestar10]

CM871 Demanded/ 11r22.5 / 13sp

Just wondering what a good cruise RPM is say for 80,000lbs right now at 67MPH in 12th im right at 1600 and i tend to run there as going to 13th drops to around 1400 and it feels like an underpowered fart.


can anyone calculate what my rear end is? when i bought the truck Int said 3.55 on website and Insite in prog-features shows 3.36 so i have no idea.

and no matter which what would be a good gear set to goto for a cruise speed between 65-70 with a buncha rolly polly hills not alot of big ones but alot of updown across i90 in soutb dakota and i80 in iowa