Cummins
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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 3.55 ratio, designed to have a proper run out with a stock size tire (roughly 31" depending on model year). But as soon as you upgrade to a 35" 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 4.23 gear ratio (3.55/31*37). Unfortunately, in this scenario there is no such thing as a 4.23 ratio, but the closest would be a 4.10 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.
Besides replacing the ring and pinion, we also offer numerous other upgrades, such as ARB Air Lockers, manual locking hub conversions, rebuild kits, ball joints, 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 cs@dieselpowerproducts.com and we would be happy to help.
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 4.23 gear ratio (3.55/31*37). Unfortunately, in this scenario there is no such thing as a 4.23 ratio, but the closest would be a 4.10 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.
Besides replacing the ring and pinion, we also offer numerous other upgrades, such as ARB Air Lockers, manual locking hub conversions, rebuild kits, ball joints, 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 cs@dieselpowerproducts.com and we would be happy to help.