Any suggestions for gear swaps to lower rpm & get better cruising mileage? I don't need fast starts, just want to drive my truck a little more. 4 speed auto diesel front axle 9.25/ rear axle 11.50/ ratio 3.73. Can you even do this without harming the drive train?

 

AAM is supposed to be releasing a 3:42 gearset, or get a gear vendors gear splitter.

 

http://www.gearvendors.com/index.html

Maybe this is an option.

 

Dropping the RPM's too low is going to do you no good...if you go to low you will be cruising out of the power band of this motor...which will make it work harder....therefore your mileage will be worse...its has been brought up on here before...you can lower it some but the splitter is too much....people i know that did it got lower RPM's and lower or the same mileage.....