Transmission's and speeds

Trucks are built for a specific job. If you were allowed to run faster, they'd have spec'd a taller rear end ratio.

 

Yes

 

Every engine has a "sweet spot" RPM where you get the best fuel economy v power. I have spoken to many mechanics and have seen most of the current specs on all the engines. This RPM never changes regardless of the rear end. Some trucks can be geared for power and some for speed. I know the general RPMs when the average truck regardless of the brand of the engine is just wasting fuel. I won't say it because I rather not start a font fight.

 

I would say older engines had a happy medium of power/fuel economy at higher RPM's than today's newer engines. While today's engines are built to perform at lower RPM's. I shake my head when I see trucks specd to run 1400-1450 at highway speeds, but I'm old school, and occasionally wrong.

 

My 2019 T680 cruises at 68 mph at 1220 rpm.

 

Older engines seemed to be happy at peak torque, these were the mechanical injection systems, electronics changed it to a flatter torque ‘curve’ and it seems the sweet spots moved a bit, 12 liter engines are higher than 15 liter engines.

 

same here, can’t imagine running a 855 at 12-1400 on a hill, I would just love to see what these new bottom ends look like being lugged everywhere.

my truck gets #### near the same milage At 62 as it does at 70 the way it’s geared, and i really don’t run enough miles to worry about fuel milage to begin with, and when it comes down to it, it’s a write off anyways

 

Sometimes time is more important than saving a few bucks on fuel.

As a new driver coming in you probably will never get to experience it, so you will never understand. But there is a special feeling when you got a lot of gears, even more chicken lights, a big cat under a long hood and your letting that big old girl eat as the sun sets on an empty prairie.

 

My X15 runs 1350 @ 70 and 1240 @ 65.