Axles - Differentials | 2011-2016 GM 6.6 Duramax LML

The 2011-2016 Duramax equipped 2500HD and 3500 trucks feature an IFS (Independent Front Suspension) AAM 9.25" assembly up front and either an AAM 11.5 or 11.8 out back. The 2011-2012 models were equipped with the long standing 11.5 that had been used since 2001, but the 2013 models were upgraded to an 11.8" ring gear for increased strength. From the factory, these housings were typically stuffed with the popular 3.73 ratio, but also had other options, such as a 4.10 used primarily for heavier towing, in most cases.

Over the years, these assemblies have proven themselves relatively reliable on moderately used trucks running stock, or close to stock tire size and power output. For those of us that demand substantial power increases and larger tires, there is room for improvement to improve the reliability and performance that they can afford. One of the best upgrades we can recommend for anyone that has increased tire size, is that of a ring and pinion ratio upgrade. As previously stated, most of these trucks came factory with a 3.73 ratio, designed to have a proper run out with a stock size tire (roughly 32"). But as soon as you upgrade to a 37" or larger tire, all of a sudden your RPM vs. speed are effected, even causing a disruption of the shift pattern on automatic transmission equipped trucks.

Lets give the example of upgrading to a 37" tire. By using cross multiplication, we can determine that in order to have the same RPM vs. speed as with the factory tire size, you would want to install a 4.31 gear ratio (3.73/32*37). Unfortunately, in this scenario there is no such thing as a 4.31 ratio, but darn close would be a 4.30 that is readily available. Or, you can also opt to go with a slightly lower ratio of 4.56 that would give you a higher RPM vs. speed compared to stock, which is especially useful for those towing frequently.

Besides replacing the ring and pinion, we also offer numerous other upgrades, such as ARB Air Lockers, rebuild kits, and so much more. As always, if you have any questions about which product is right for you and your truck don't hesitate to give us a call or send us an e-mail to [email protected] and we would be happy to help.

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