There's a fine line between 'better' and 'worse'. with 3.73's and 34's...even though you are spinning less rpms, you are putting more of a load on the engine, thus creating larger fuel consumption. at highway speeds...the motor is working so hard to keep the darn thing moving that you lose any and all 'gains' you might have got. reason being, is that the rpms drop so much, that you are out of your powerband where the torque output at highway speeds have been lowered, and it's harder for the truck to 'keep speed'.
4.0L sohc + 3.73 + 35's = massive suckage of fuel and drivability.
my truck with the 4.0L sohc, 35's, and 4.10s was fine in the fuel department...but the truck completely sucked on freeway runs. the darn thing wouldn't 'keep speed' on the highway...no torque at all in 5th gear and going 65.
'01 XLT disguised as a '03 Fx4 Level II
Big. Loud. Slow. Bright.