You will not ABSOLUTELY lose mileage with the 3.92. They multiple power and can actually make the truck MORE efficient, as needs less gas pedal to do the same work. Where the efficiency in the deeper gear is lost is at the very top end where the RPM of the truck can't settle as deep as it can with a higher gear (numerically lower).
Deeper gears (numerically higher) offer free power, yielding more responsiveness at all speeds and rpms. The LSD makes no difference.
Deeper gears (numerically higher) offer free power, yielding more responsiveness at all speeds and rpms. The LSD makes no difference.
