My uncle has a 2009 2500 6.7l quad cab with 4x4 and a 6MT (not sure which axle ratio he has). He says that the 6th gear isn't tall enough. Are there any underdrive/overdrive units that are available for this truck? He also mentioned something about a hand held tuner that provided different settings for increased gas mileage and/or performance. I've known about bulley dog but I couldn't find anything like this on their website. Any other MPG mods that would be worthwhile?

 

only thing to take care of 6th gear is to change your rear end gears.

Anytime you change the intake, exhuast you will get better fuel milage cause its breathing better.

Programmers sometimes will make it a bit better but most of the time your foot gets heavy with them and ends up using more haha.

You can get a bully dog, superchips, edge, smarty, banks, DSP, there are alot out there

 

if you wanna see a big difference in MPGs delete the dpf and egr systems