Need some help deciding if you should change the gear ratio in your Duramax diesel? Changing the ratio to compensate for your larger tires will help improve fuel economy, lower EGT temps, restore towing performance, and put less stress on your transmission and drivetrain. Here is some first hand experience from the Dmaxstore team.

2006-2015 : Duramax trucks with 6 speed Allison, Stock Ratio is 3:73

32"-34" Tall tires we recommend running a 4:10 gear ratio. This will put you back to stock with 33" tires. With 32" tires you will be slightly lower than stock.

35"-36" Tall tires we recommend running a 4:56 gear ratio. This will put you back to stock with 36" tires. With 35" tires you will be slightly lower than stock.

37"-42" Tall tires we recommend running a 4:88 gear ratio. With 37" tires you will be slightly lower than stock. However we recommend being lower than stock to help correct the heavy weight of these large tires.