To find the gear ratio for *your* specific 2010 Dodge Cummins 3500, you need to check one of the following:
* The sticker on the driver's side doorjamb: This sticker often lists the axle ratio.
* The owner's manual: It may specify the axle ratio.
* The build sheet (if you have it): This document details the specifications of your truck.
* The vehicle's identification number (VIN): A dealer or parts specialist can use the VIN to access the truck's build information, including the axle ratio.
Without more specific information about your truck, it's impossible to provide the correct gear ratio.