Run the truck in 3rd, not D. That will give you a much better gear ratio then what you have in OD now. I bet it down shifts all the time! Down shifting all the time will cause HORRIBLE mileage. Just leave it in 3rd. 3rd with current gears will be like D with lower gears.

Oh and get your PCM recalibrate for the correct tire size! You really don't know what mileage your getting cuz the odometer is not reading right.

 

He still should gear up though. While you're completely correct, that's still a bandaid solution for a truck that's way undergeared for big tires. 4.56s and a tune (both for performance and to correct the speedo/odometer) will straighten his truck right out.

 

And he might as well wait until after the gears to get the tune anyway cuz he's going to have to alter the gear ration in the computer afterward anyway; then he'll only have to visit the tuner once

 

The only difference from running in 3rd instead of D with the current gears is that 1st is not as low as if he regeared. 1st is really low in these tranys anyway, And its a lot cheaper then buying new gears for the same affect.

 

I have 3.73s with 33s and the low first gear with no issues. I'm even considering gears myself. His setup, even in 1st gear, doesn't even come close to having nearly as much torque as my setup, and I want more. You're right, picking a lower gear to cruise in would help him a lot on the highway, but it won't help him around town. He could manually shift all the time, I guess. Yeah, gears are expensive, but you gotta pay to play. Big tires mean gears or big power, sometimes a little bit of both, and a tune to reset the tire size is a must.

 

By the way I have the super-low first gear (6L80E)

 

ok must of been how I was driving it, dried it more normal this tank, easier on the skinny pedal and i got about 230miles to this tank, not nearly as bad, and my truck has 3;73 not 3;42, I remember when I hat the 5.3 i could get close to 300 miles a tank with 35's but only a 3 body lift, either way Im not complaining now as its not my dd

 

Did you get the PCM recalibrated? If not, and your old tires were 30 inches tall, then 230 miles is actually closer to 275 miles.