3:55 to 3:08, opinions?

Wow. My 500 hp DDEC IV Series 60 does real stellar on fuel mileage in the 1350-1400 rpm range. It does pretty well at 1500 working serious hills. If I ran it at 1600 it would take a hit. Averaging low to mid 7's on winter fuel with heavier loads. With lighter loads and summer fuel, it gets into solid 8 mpg territory often. I haven't modified the ECM yet (waiting till after I run the first overhead at 60,000 in a few weeks), but do have ported/coated exhaust manifold, larger Borg Warner 171702 non-wastegate turbo with a blanket, and Walker Megaflows on the stacks. Guess each engine is different.

 

I just want to know will 3.08 gear ratio and super 40 differ in semi be okay to haul 130k lbs gross weight.

 

yes with about 1000 hp