Originally Posted by Rangers13
What kind of mpg difference can one expect between the 3.21/3.55/3.92 when paired with the 8sp?
This is so heavily dependent on individual drivers, their weather, their terrain, their altitude, and how much they carry or tow, and which truck and options they have.
Put my best guess if all being exactly equal, on average you'd see a
.5-.75 mpg drop between the axle ratios.
So two exact trucks, the one with the 3.92's would expect to get 1-1.5 mpg less gas mileage than one with a 3.21